Helix bicarinata G. B. Sowerby I, 1824 = Hystricella bicarinata (G. B. Sowerby I, 1824).

Lowe (1855: 186–187) describes the new genus Hystricella in the section § 24, basing his description upon shell features only, as follows:

(Typ. H. bicarinata, Sow.). T. perf. v. angustae umbil. conuloidea v. trochiformis, aliquando turrito-pyramidata acute v. distincte 1–2-carinata solidiuscula aspero-granulata v. echinulata subfasciata. Anfr. 6–9 lente crescentes planiusculi, ult. valde carinato subtus planato, antice deflexo. Umbil. parvus anguste cylindricus v. subspiralis constrictus. Apert. circularis circinata labris connexis; perist. continuum solutum expanso-reflexiusculum tenue acutum.

Lowe (1855: 186–187) cites for the genus (under section § 24) the following species:

H. bicarinata G. B. Sowerby I, 1824

H. echinulata R. T. Lowe, 1831

H. oxytropis R. T. Lowe, 1831

H. turricula R. T. Lowe, 1831

H. vermetiformis R. T. Lowe, 1855

Hystricella mustelina Reeve, 1854 [under authorship R. T. Lowe, 1855], currently considered as a subspecies of Discula (Discula) cheiranthicola Reeve, 1854 [even though the description was prepared by R. T. Lowe in 1854 the work was only published in 1855 and therefore the earlier publication of that name in Reeve in 1854 has priority].

Hystricella cheiranticola R. T. Lowe, 1831 and its morphae (later put in the mono-specific subgenus [as section] Turritella by Wollaston 1878 [non Lamarck 1799]).

Later, H. mustelina (currently Discula (Discula) cheiranthicola mustelina (Reeve, 1854)) and H. cheiranticola (currently Discula (Discula) cheiranthicola cheiranthicola (R. T. Lowe, 1831)) were assigned to the genus Discula R. T. Lowe, 1852 (Mandahl-Barth 1950).

Shell. The shell is dextral, hairless and it is usually conical and scalariform. The protoconch is whitish to dark brown, with 1.3 to 2.2 whorls. It is almost smooth along the first whorl and shows fine radial striae and extremely small, scattered tubercles along its remaining portion. The teleoconch has from 4.2 to 5.0 rapidly increasing whorls. It is usually dark brown with brick red and/or dark violet colour shades. The dark areas of the shell are mottled with more or less light brown to whitish areas, usually placed longitudinally and slightly slanting. No band pattern is visible along the upper whorls. On the lower part of the last whorl two well-defined, dark bands are visible that can differ in width. The area around the umbilicus is usually the lightest in colour. The spire is slightly variable in height, ranging in shape from compressed to somewhat more elevated. Along the last and the penultimate whorls one to two evident keels are present. The external upper surface has very fine but clearly visible, irregularly spaced growth lines. Along the last whorls the growth lines usually disappear along the lateral area and reappear on the lower part. Irregularly disposed tubercles are found all over the teleoconch. The dimensions of the tubercles tend to increase slightly from the first toward the last whorl, the density remaining, however, approximately the same. The tubercles are somewhat denser along the keels of the penultimate and last whorls, letting the keel/keels appear like a rough chord. On the lower part of the last whorl the tubercles are usually bigger and slightly less dense than in the remaining parts of the shell. The last whorl is large, with a contribution of 60% of the total shell height and descending towards the aperture. The umbilicus is open but very narrow, concentric and has a diameter of approximately 10% of the maximum shell diameter. The aperture is elliptical with a faint thickening along the inner side of the last whorl. The peristome is continuous, slightly reflected with the columellar margin somewhat thicker and more reflected.

Body. Head and neck are grey to pale grey, slightly transparent. The sides and posterior upper section of the foot are whitish. The sole of the foot is whitish and longitudinally divided into three areas. The central area is smooth whereas the two lateral areas are equipped with bands of muscles roughly arranged in a chevron pattern. The mantle border is grey to dark grey with five more or less developed lobes. The ratio among lateral and dorsal lobes varies from specimen to specimen also in the same population. In some specimens, particular lobes (regardless if lateral or dorsal) may be completely missing. The walls of the pallial cavity are colourless, without any stripes or spots. A strong pulmonary vein is visible.

Genitalia. The general arrangement of the genitalia is semi-diaulic monotrematic. A convoluted to almost straight first hermaphroditic duct arises from a multi-lobated gonad. The albumen gland is long and moderately thin and connected to an equally long sperm-oviduct consisting of a prostatic and a uterine portion. Distally, the prostatic part extends into a thin vas deferens, twice as long as the sperm-oviduct, terminating in the penial complex. The distal portion of the uterine part inserts into the free oviduct, then transforming into a vagina at the level of the insertion of the duct of the bursa copulatrix. The free oviduct is usually three to four times shorter than the vagina. The duct of the bursa copulatrix is usually wide, approximately as long as the penis and uniform in diameter. This duct terminates in a variable, oval to roundish, small bursa copulatrix. The spermatophore is unknown. One tuft of digitiform glands arises from the proximal part of the vagina. There are usually two or three, equally long and very rarely branched glands. A short and thin vaginal appendix arises from the vagina’s wall, immediately distal of the glandular tuft. Very smooth, little elevated and spaced pleats run longitudinally along the inner surface of the vagina, reaching into the genital atrium as far as the genital orifice. The atrium can be short or moderately long. The penial complex consists of a flagellum, an epiphallus (which extends from insertion of the vas deferens to the penial retractor muscle) and a penis that inserts into the genital atrium. The penial flagellum is short, remarkably cylindrical and with a blunt apex. It is usually twice as long as the epiphallus. Its internal walls can be either completely smooth or ornamented with very small papillae distributed mainly close to the blunt end. The epiphallus is usually extremely short and its internal walls are smooth. The retractor muscle is well developed, strong and is variable in length. The penis lacks a muscular or glandular sheath. It is thick-walled and approximately four times longer than the flagellum. It is usually cylindrical to sometimes slightly swollen in its distal part. The inner walls of the penis are usually smooth or with very smooth, little elevated and spaced pleats which run longitudinally and reach the genital atrium. The section where the penial papilla is located is usually detectable from the outside by virtue of a fine circular swelling corresponding to the origin of the papilla itself. The penial papilla is very variable in size, ranging from 1/6 to 1/2 of the total penial length and is conical to subcylindrical in shape. The inner lumen of the penial papilla is filled with a spongy and sturdy tissue which directly connects with the walls of the epiphallus. It has smooth external walls with the opening emerging apically. The channel of the penial papilla is thin and narrow. The longitudinal section of the penial papilla shows that its walls are the continuation of the penial walls that abruptly bend inward.

Jaw and radula. The jaw and radular apparatus of Hystricella is depicted in Fig. 8. No notable variability was found among the species of the genus. The jaw is odontognathous, almost straight to markedly arched, with 13 to 15 smooth ridges. The radula ribbon is typical helicoid, it is elongated but not very slender. Central tooth present, tricuspid, the main cusp (endocone) is rhomboid, pointed; the ectocones are much smaller than the endocone; they are triangular, pointed. There are 19–20 laterals and marginals which do not distinctly differ from each other, i.e., their shape changes gradually from the first laterals towards the marginals. Laterals are bicuspid, endocones are rhomboid or triangular and pointed. The ectocones are much smaller, pointed, and triangular. The endocones of the central tooth and the first laterals are approximately of the same size. Both, the endocone and the ectocone of the laterals gradually become bifurcated towards the marginal teeth, but the ectocones may occasionally have three cusps as well. The cusps of the marginals are gradually decreasing in size; therefore, the outermost marginals appear nearly serrated.

The genus Hystricella is endemic to the island of Porto Santo (Madeiran Archipelago, Portugal). The genus is restricted to the eastern, mountainous part of the island and occurs there only in the central-northern section of this area (Fig. 7). Species assigned to the genus are commonly found on the slopes of Pico do Castelo, Pico do Facho, Pico de Juliana, Pico da Gandaia, Rocha de Nossa Senhora, the western slopes of Pico do Concelho, and those of the Pico Branco and Terra Chã complex. It is also commonly found at lower elevations of Serra de Dentro, Barranco Branco, and Lombo de Paredes. Recent Hystricella are absent from the southeastern part of the island, i.e., from Vale do Touro, Portela, Pico do Maçarico, and Pico do Baixo. It is likewise not present on the small islets surrounding the main island, namely Ilhéu de Cima, Ilhéu de Baixo, and Ilhéu de Ferro. Subfossil representatives of the genus are found mainly in the mud and aeolinite deposits along the southeastern coast, namely Vale do Touro, Ponta do Passo, Barbinha, and Calhau da Serra de Fora.

Figure 7. 

Distribution of the genus Hystricella. Filled circles refer to recent and open circles to fossil records.

Figure 8. 

Radulae and jaws of Hystricella species. A Hystricella bicarinata, Ribeira da Areia B Hystricella echinulata, path to Pico Branco.

Representatives of the genus Hystricella are commonly found under volcanic rocks scattered on grassland in open fields that are more or less strongly sloping. They have been found under stones in pine woods (Pico do Castelo) or in cracks and crevices of rocky walls (Pico da Gandaia). Disturbed or anthropogenic habitats have also been colonised by representatives of the genus, such as stone walls (Pedregal de Dentro) or terraced areas (southern slopes of Pico do Castelo). Specimens aestivate on the lower surfaces of stones or rocks, frequently forming large clusters of individuals attached to one another, reaching more than 40 to 50 in number. Under a single stone of roughly 60 × 40 cm approximately 200 individuals were counted (southern slopes of Pico do Facho).

Hystricella was considered a subgenus of Helix for a long time (until Wollaston 1878) or was replaced by Ochthephila Beck, 1837 (Albers 1850) or Octephila Paiva, 1867 (Paiva 1867). Later it was considered as a subgenus of Discula R. T. Lowe, 1852 and only since 2002 (Bank et al. 2002) accepted as a distinct genus.

Bank et al. (2002) used the generic name Geomitra Swainson, 1840 despite Herrmannsen’s (1847: 470) selection of the nominal species Helix tiarella Webb & Berthelot, 1833 as the type species of that genus. The decision of Herrmannsen was followed by all subsequent authors (e.g., Wollaston 1878; Mandahl-Barth 1950; Waldén 1983). The reason to contradict that type selection was the fact that it was wrong with respect to the rules of the International Commission on Zoological Nomenclature’s (ICZN) Code of Zoological Nomenclature (hereafter ‘the Code’) Art. 67.2.1: Swainson introduced Geomitra describing and depicting tiarella, namely on p. 166 and 332, but he did not mention that name, but instead only bicarinata, which therefore would be the type species by monotypy. In consequence Hystricella R. T. Lowe, 1855 would become a synonym of Geomitra and Geomitrasensu auct. has to be referred to Craspedaria R. T. Lowe, 1852. Nevertheless, this decision was much criticised (Seddon 2008) and a new study of the Code revealed a solution which permits the stabilisation of the former use of Geomitra (Groh et al. 2009). Following Art. 70.3 of the Code the combination of the figure of tiarella with the name bicarinata can be interpreted as a misidentification by Swainson and therefore following Art. 70.3.2, the name tiarella becomes available for type selection under the synonymous name Geomitra bicarinata Swainson, 1840. This was already recognised by Pfeiffer (1847: 191) who listed Swainson’s combination as a synonym of Helix tiarella (cf. Groh et al. 2009).

Hystricella shows a number of morphological characters that clearly distinguishes it from the other native geomitrid genera from Porto Santo, in particular with regard to the genus Discula s. lat., into which the Hystricella species were previously placed (Mandahl-Barth 1950; Waldén 1983). On the basis of the shell, the main distinguishing feature of Hystricella from Discula s. lat. is the continuous and detached peristome. On the contrary, in Discula s. lat. and Callina (Figs 10–12) the peristome is always interrupted, forming only a thickening or a callous along the parietal region but not a real and proper detached lip. Other minor differences can be found in the ornamentation of the shell’s surface. Hystricella always possesses round, somewhat spaced tubercles, whereas Discula s. lat. and Callina shows mainly elongated, sometimes drop-like tubercles arranged in a regular pattern. In Hystricella the size of the tubercles can reach large dimensions in comparison to the overall size of the shell and their size can remarkably vary on the same shell. Actinella s. lat. and Caseolus s. lat. (see Figs 13–16) also possess an interrupted peristome. Most Caseolus species have a more or less granulated shell’s surface and, at first glance, could therefore be confused with Hystricella. However, a closer look reveals the different peristome and the overall different shape, with the whorls always rounded and usually without any prominent keel. Serratorotula (Fig. 17) has an extremely ornamented shell that is easily distinguishable from Hystricella. The shell form of Heterostoma is very different from that of Hystricella and these two genera are therefore easily distinguishable (see Seddon 2008: 125). Some species of the genus Spirorbula sometimes have shells with a continuous peristome with detached lips along the parietal side. The very depressed shell shape and different surface ornamentation of Spirorbula however, readily distinguishes the two genera (Fig. 18). Lemniscia usually possesses a smooth and rather glossy shell without tubercles or papillae (Fig. 19). The shell morphology of Wollastonia gen. n. and its differences with regard to Hystricella will be discussed in the section on Wollastonia gen. n. below.

Figures 9–19. 

Shells of Portosanctan and Madeiran Geomitridae. 9 Hystricella bicarinata, Pico do Castelo, S slope around the Miradouro 10 Discula discina, Porto da Morena 11Discula (Mandahlia) tectiformis, Pico do Baixo 12 Callina rotula, Cabeco dos Bades 13Actinella (Plebecula) littorinella, E of Pico do Castelo 14Caseolus (C.) innominatus portosanctanus, Ribeira da Areia 15Caseolus (Helicomela) punctulatus punctulatus, Fonte da Areia 16Caseolus (Leptostictea) leptosticus, Ponta do Garajau, Madeira 17 Serratorotula juliformis, Pico de Ana Ferreira 18 Spirorbula depauperata, Pico de Ana Ferreira 19 Lemniscia michaudi, Terra Chã. Scale bar: 1 cm.

With regard to genital morphology, Hystricella shows a unique feature that allows the separation of the genus from all native Portosanctan Geomitridae, except from Wollastonia gen. n. The main difference is the shape of the penial flagellum which is always short and has a remarkably blunt apex (Fig. 20). Discula s. lat. and Callina, Serratorotula, and Lemniscia (Figs 21–25) have a pointed, more or less elongated flagellum. Hystricella is easily distinguishable from Caseolus s. lat. and Actinella s. lat. by virtue of the single vaginal appendages instead of the two that are present in these genera (see Figs 26–29). Spirorbula is also easily distinguishable from Hystricella because members of this genus possess two extremely long, and sometimes branched, vaginal appendages and a genital atrium with structures on the inner wall consisting of large and partially fringed folds (see Fig. 30).

Figures 20–30. 

Outer distal genitalia of Portosanctan and Madeiran Geomitridae. 20 Hystricella bicarinata, Capela da Graça 21 Discula polymorpha alleniana, Porto Moniz, Madeira 22Discula (Mandahlia) tectiformis, Pico do Baixo 23 Callina rotula, Cabeco dos Bades 24 Serratorotula juliformis, Pico de Ana Ferreira 25 Lemniscia michaudi, Terra Chã 26Actinella (Plebecula) littorinella E of Pico do Castelo 27Caseolus (C.) innominatus portosanctanus, Ribeira da Areia 28Caseolus (Helicomela) punctulatus punctulatus, Fonte da Areia 29Caseolus (Leptostictea) leptosticus, Ponta do Garajau, Madeira 30 Spirorbula depauperata, Pico de Ana Ferreira. Scale bars 1 mm.

1824 Helix bicarinata G. B. Sowerby I: 58, pl. 3 fig. 7.

1828 Helix bicarinata – Wood: pl. 8 fig. 85.

1831 Helix duplicata R. T. Lowe: 58, pl. 6 fig. 30 [unjustified replacement name for Helix bicarinata Sowerby I, 1824 [non Helix C.[ochlitoma] bicarinata J. Férussac, 1821, a secondary homonym of Bulimus bicarinatus Bruguière, 1792 = Archachatina bicarinata (Bruguière, 1792). See Taxonomic Remarks below].

1846 Helix bicarinata – L. Pfeiffer: 141, pl. 91 figs 8–11.

1847 Helix bicarinata – L. Pfeiffer in L. Pfeiffer 1847–1848: 190.

1854 Helix bicarinata – Reeve in Reeve 1851–1854: pl. 142 figs 908–909.

1854 Helix (Ochthephila) bicarinata – Albers: pl. 9 figs 1–4.

1855 Helix (Hystricella) bicarinata – R. T. Lowe: 186.

1867 Helix (Octephila) bicarinata – Paiva: 45.

1878 Helix (Hystricella) bicarinata – Wollaston: 161–163.

1888 Helix bicarinata – Tryon in Tryon and [Pilsbry] 1888: 33, pl. 7 fig. 90.

1894 Geomitra bicarinata – Pilsbry in Pilsbry 1893–1895: 242.

1931 Geomitra (Actinella) bicarnata – Nobre: fig. 37.

1950 Discula (Hystricella) bicarinata bicarinata – Mandahl-Barth 1950: 31, 55.

1966 Discula (Hystricella) bicarinata – S. G. A. Jaeckel: 53.

1983 Discula (Hystricella) bicarinata bicarinata – Waldén: 267.

2002 Geomitra bicarinata bicarinata – Bank et al.: 124.

2008 Hystricella bicarinata – Seddon: 79, pl. 29 fig. E, map 178.

2011 Hystricella bicarinata – Seddon: e.T6724A12800659.

Despite intensive research in multiple museum collections (NHM, NMW, MMUE, ANSP, NHC, NMS, OUMNH, RAM, SMF) that could have held the type material of the taxon, no such material could be traced and therefore we deem it reasonable to assume that the type material is lost. To stabilise the present interpretation of Helix bicarinata G. B. Sowerby I, 1824 and to clarify its taxonomic status we designate a neotype here, which is deposited in the collection of the SMF under the No. SMF 348936 (see Fig. 33). The original figures of Helix bicarinata G. B. Sowerby I, 1824 from Sowerby (1824: pl. 3 fig. 7) 32 and Helix duplicata R. T. Lowe, 1831 from R. T. Lowe (1831: pl. 6 fig. 20) are depicted in Figs 31–32. The neotype (Fig. 33) is consistent with the figure in Sowerby (1824: pl. 3 fig. 7) and the original description (see below), especially with regard to size, shape and the presence of two keels on the body whorl. The taxon was originally described from Porto Santo without more detailed locality data, which is consistent with origin of the specimen selected as neotype.

Figures 31–32. 

31 Original figure of Helix bicarinata G. B. Sowerby I, 1824 from Sowerby (1824: pl. 3 fig. 7) 32 Original figure of Helix duplicata R. T. Lowe, 1831 from R. T. Lowe (1831: pl. 6 fig. 20).

Pico do Castelo, S slope around the Miradouro, under stones in pine wood, 33°04'42"N/16°20'00"W, 270 m (through the designation of the neotype).

All from Porto Santo, ANSP H 20185/13, NW slope of Pico Branco, 33°05'50"N/16°18'57"W to 33°05'52"N/16°18'49"W, 150–200 m, leg. J. & C. Hemmen, Jan. 8 1981; ANSP H 11776/2, NW slope of Pico de Juliana, 33°05'34"N/16°19'25"W, up to 450 m, leg. J. & C. Hemmen, Jan. 6 1981; CKG/12, Pico de Juliana, under stones, 33°05'31"N/16°19'20"W, 365 m, leg. K. Groh, Jun. 23 1983; ANSP H 11788/11, CMN/3, SW slope of Pico do Juliana, 33°05'30"N/16°19'23"W, 360 m, leg. J. Gerber, K. Groh & J. Hemmen, Aug. 13 1985; CFW 11149/1, Pico Juliana, old quarry on the southern slope, 33°05'28"N/16°19'17"W, 330 m, leg. F. Walther & E. M. Gryl, Apr. 3 2017; ANSP H 11769/3, Ribeiro das Esmoitadas (E Camacha), 33°05'27"N/16°20'17"W, 130 m, leg. J. Gerber, K. Groh & J. Hemmen, Aug. 13 1985; CKG/2, SW of Pico de Juliana, 33°05'14"N/16°19'32"W, 360 m, leg. K. & C. Groh, Oct. 27 1980; CFW 11158/10, Pico do Facho, NW slope, 33°05'12"N, 16°19'38"W, 370 m, leg. F. Walther, Apr. 3 2017; ANSP H 20186/1, NE slope of Pico do Facho, 33°05'07"N/16°19'23"W, 430–450 m, leg. K. Groh & J. Hemmen, Jun. 28 1983; CWDM/6, CMN/ 3, ridge between Pico do Facho and Pico da Gandaia, stone walls, 33°05'04"N/16°19'21"W, 460 m, leg. W. De Mattia & J. Macor, May 25 2015; CWDM/15, N slope of Pico do Facho in Tamarix wood, under stones, 33°05'04"N/16°19'25"W, 475 m, leg. W. De Mattia & J. Macor, May 25 2015; CKG/44, CMN/6, W of Pico do Facho, under stones, 33°05'04"N/16°19'33"W, 450 m, leg. K. Groh, Jun. 29 1983; ANSP H 11778/c. 40, SW slope of Pico do Facho, 33°05'03"N/16°19'31"W, 460–480 m, leg. K. Groh & J. Hemmen, Jun. 28 1983; CKG/24, CMN/44, upper Ribeira Formosa between Covau and Serra de Fora, under stones, 33°05'02"N/16°19'14"W, 140 m, leg. K. Groh, Jun. 19 1983; ANSP H 11775/13, W slope of Pico do Facho, 33°05'02"N/16°19'38"W, leg. J. & C. Hemmen, Jan. 6 1981; ANSP H 11834/19 [sub H. echinulata], summit of Pico da Gandaia, 33°05'01"N/16°19'14"W, 440 m, leg. J. & C. Hemmen, Jan. 6 1981; CWDM/11, CMN/7, Pico da Gandaia, southern rocky cliffs close to the top, under stones, 33°05'01"N/16°19'14"W, 440 m, leg. W. De Mattia & J. Macor, May 25 2015; ANSP H 11779/24, SW slope of Pico do Facho, 33°04'56"N/16°19'39"W to 33°05'02"N/16°19'30"W, 300–450 m, leg. K. Groh & J. Hemmen, Jul. 1 1983; CWDM/15, CMN/3, N and E slopes and summit of Pico do Castelo, under stones in pine wood, 33°04'55"N/16°20'07"W, 350 m, leg. W. De Mattia & J. Macor, May 22 2015; CWDM/25, CMN/5, S slope of Pico do Facho, along path at the S border of the pine wood, under stones, 33°04'52"N/16°19'26"W, 355 m, leg. W. De Mattia & J. Macor, May 17 2015; CKG/8, Pico do Castelo, S slope around the Miradouro, under stones in pine wood, 33°04'51"N/16°20'03"W, 420 m, leg. K. & C. Groh, Oct. 27 1980; CWDM/22, CMN/4, Ribeira da Areia, serpentine 240 m NNW the quarry, under stones, 33°04'51"N/16°18'41"W, 140 m, leg. W. De Mattia & J. Macor, May 21 2014; ANSP H 11787/c. 30, approx. 1 km NE Capela da Graça, 33°04'49"N/16°19'04"W, 250 m, leg. J. & C. Hemmen, Jan. 4 1981; CWDM/12, CMN/4, lake shore S of Ribeira da Serra de Dentro, under stones and in stone walls, 33°04'48"N/16°18'31"W, 70 m, leg. W. De Mattia & J. Macor, May 22 2015; ANSP H 20187/1, NW slope of Pico do Concelho, 33°04'44"N/16°18'04"W to 33°04'43"N/16°18'01"W, 250–300 m, leg. K. Groh & J. Hemmen, Jul. 29 1983; CKG/8, CMN/8, Pico do Concelho, NW of the top, under stones, 33°04'43"N/16°17'59"W, 260 m, leg. K. Groh, Jun. 29 1983; ANSP H 11835/12 [sub H. echinulata], NW slope of Pico do Concelho, 33°04'43"N/16°18'01"W, approx. 280 m, leg. J. & C. Hemmen, Jan. 6 1981; ANSP H 12780/32, NW slope of Pico do Concelho, 33°04'43"N/16°18'01"W, 250–300 m, leg. K. Groh & J. Hemmen, Jun. 6 1983; CWDM/15, CMN/2, summit of Pico do Concelho, under stones, 33°04'42"N/16°18'01"W, 280 m, leg. W. De Mattia & J. Macor, May 18 2015; CWDM/18,CMN/4, Pico do Castelo, S slope around the Miradouro, under stones in pine wood, 33°04'42"N/16°20'00"W, 270 m, leg. W. De Mattia & J. Macor, Feb. 12 2012; CMN/1, Pico do Castelo, S slope around the Miradouro, under stones in pine wood, N slope, 33°04'42"N/16°20'01"W to 33°04'51"N/16°20'03"W, 300–430 m, leg. K. Groh Jul. 1 1983; ANSP H 11783/24, Pico do Castelo, 33°04'42"N/16°20'01"W to 33°04'51"N/16°20'03"W, 350–430 m, leg. K. Groh & J. Hemmen, Jul. 1 1983; CWDM/8, CMN/4, path from Capela da Graça to Pico do Castelo along the Levada, under stones, 33°04'38"N/16°19'48"W, 165 m, leg. W. De Mattia & J. Macor, May 17 2015; CKG/3, CMN/68, Capela da Graça up to Pico de Facho-Motos de Fora, under stones, 33°04'38"N/16°19'33"W, 200 m, leg. K. Groh, Jun. 23 1983; ANSP H 11785/9 spms, Ribeiro do Formoso, 33°04'36"N/16°19'04"W, 130 m, leg. J. Gerber, K. Groh & J. Hemmen, Aug. 13 1985; ANSP H 11777/12, approx. 1 km S Serra de Dentro, 33°04'33"N/16°18'25"W, 160 m, leg. J. & C. Hemmen, Jan. 8 1981; ANSP H 11782/c. 30, slope between the SE slope of Pico do Castelo and Capela da Graça, 33°04'32"N/16°19'38"W, 160 m, leg. J. & C. Hemmen, Jan. 4 1981; CFW 11161/7, Casinhas, N of Capela da Graça, 33°04'27"N/16°19'27"W, 150 m, leg. F. Walther, Apr. 4 2017; CKG/11, CMN/1, Pico do Baixo, 33°04'26"N/16°19'44"W to 33°04'46"N/16°19'44"W, 100–250 m, leg. K. Groh, Jul. 11, 1983; CWDM/23, Engula, under stones, 33°04'19"N/16°19'01"W, 150 m, leg. W. De Mattia & J. Macor, May 18 2015; CFW 11159/>10, E slope of Rocha de Nossa Senhora, 33°04'19"N/16°19'01"W, 150 m, leg. F. Walther, Apr. 3 2017 ANSP H 11771/18, N of Portela (E of Vila Baleira), 33°04'07"N/16°19'17"W, 120 m, leg. J. & C. Hemmen, Jan. 4 1981; CKG/2, CMN/1, Capela da Graça up to Pico do Facho-Motos de Fora, N slope, 33°04'38"N/16°19'33"W to 33°05'04"N/16°19'33"W, approx. 200–450 m, leg. J. Gerber, K. Groh & J. Hemmen, Jun. 28 1985; ZMH 120610/2, foot of Pico do Castelo, c. 33°04'37"N/16°19'49"W, 170 m, ex coll. W. Fauer, leg. J. & C. Hemmen, Jul. 11 1983; ZMH 110165/68, slopes of Pico do Facho, under stones; c. 33°04'59"N/16°19'25"W, 430 m a.s.l., leg. E. Clauss, Sep. 22 1992; ZMH 24288/2, Madeira Archipelago, without exact locality data, ex coll. Altonaer Museum; ZMH, 24289/1, Porto Santo, without exact locality data, ex coll. Museum Klagenfurt; ZMH 24290/3, Porto Santo, without exact locality data, ex coll. Altonaer Museum, ex coll. O. Semper, ex coll. Dohrn.

From Sowerby (1824): testa subglobosa, spira breviuscula, subconica; anfractibus quinque quadratis, mediane carinis duabus, superiore obtusiuscula: apertura integra, rotunda, peristomate distincto: umbilico parvo. Axis ³∕₁₆, diam. ¼ unc.

Shell as in the genus description. The main diagnostic feature is the presence of two well-developed keels along the penultimate and body whorl. The lower keel is usually slightly stronger and more evident than the upper one along both whorls. The overall shape of the shell of Hystricella bicarinata is always conical and scalariform by virtue of a “shoulder” that lets the contour of the whorls appear markedly angular. The sutures are deep and well-marked (see Figs 33–37).

Figures 33–37. 

Shells of Hystricella bicarinata. 33 neotype of Hystricella bicarinata, Pico do Castelo, S slope around the Miradouro, SMF 348936 34 syntype of H. duplicata R. T. Lowe 1831, NHM 1948.7.8.34; Shells of Hystricella bicarinata 35 Capela da Graça 36 Pico do Castelo, S slope around the Miradouro 37 Pico da Gandaia. Scale bar 1 mm.

D 4.9 ± 0.2 mm (range 4.4–5.3 mm); H 3.8 ± 0.2 mm (range 3.4–4.2 mm); FW 2.4 ± 0.2 mm; PA 53.5 ± 2.4°; DU 0.4 ± 0.09 mm; NT 21 ± 6; NW 5.6 ± 0.1 (range 5.1–5.75) (n = 40). Ratio D/H 1.3; ratio FW/H 0.6.

Body as in the genus description.

As in the genus description. The albumen gland is long and connected to an equally long sperm-oviduct. The prostatic part extends into a thin vas deferens that is twice as long as the sperm-oviduct. The free oviduct is somewhat variable in length, but is usually three to four times shorter than the vagina. The duct of the bursa copulatrix is usually wide, slightly shorter than the penis, opening out into a roundish, small bursa copulatrix. One tuft of digitiform glands consisting of two, more rarely three never branching glands. The inner ornamentation of the vagina consists of very wide, low, and smooth pleats running longitudinally as far as the genital atrium. The penial flagellum is short, remarkably cylindrical and with a blunt apex. It is usually as long as the epiphallus. Its internal walls are completely smooth. The epiphallus is short and its internal walls are smooth. The penis lacks any muscular or glandular sheath. It is thick-walled and approximately four times longer than the flagellum. It is cylindrical and sometimes slightly swollen in its distal part. The inner walls of the penis are usually smooth or with very smooth, little elevated and spaced pleats which run longitudinally and reach the genital atrium (see Figs 38–53).

Figures 38–45. 

Genitalia and anatomy of Hystricella bicarinata. Pico do Castelo, S slope around the Miradouro: 38 whole genitalia excluding part of OSD, AG and gonads 39 ornamentation of the inner walls of the distal penis, the vagina and the genital atrium 40 transverse section of penial papilla. Pico da Gandaia: 41 whole genitalia excluding gonads 42 ornamentation of the inner walls of the flagellum, the penial complex, the vagina and the genital atrium. Ribeira de Serra de Dentro: 43 jaw. Pico da Gandaia: 44 mantle border. Ribeira de Serra de Dentro: 45 whole genitalia excluding part of OSD, AG and gonads. Scale bars 1 mm.

Figures 46–53. 

Genitalia and anatomy of Hystricella bicarinata. Capela de Graça: 46 whole genitalia excluding part of OSD, AG and gonads 47 penial papilla 48 longitudinal section of the penial papilla 49 ornamentation of the inner walls of the flagellum, the penial complex, the vagina and the genital atrium. Ridge between Pico do Facho and Pico da Gandaia: 50 whole genitalia excluding part of OSD, AG and gonads. NE slopes of Pico do Castelo: 51 section of vagina. Capela da Graça: 52 jaw. S slopes Pico do Facho: 53 mantle border. Scale bars 1 mm.

Hystricella bicarinata is endemic to the island of Porto Santo (Madeiran Archipelago, Portugal) (Fig. 54). The species is restricted to the eastern, mountainous part of the island and is present only in the central section of this area. It is commonly found on the slopes of Pico do Castelo, Pico do Facho, Pico de Juliana, Pico da Gandaia, Rocha de Nossa Senhora, and the western slopes of Pico do Concelho. It is also commonly found at lower elevations of the Serra de Dentro, Barranco Branco, and Lombo de Paredes. It is not present on the small islets surrounding the main island, namely Ilhéu de Cima, Ilhéu de Baixo, and Ilhéu de Ferro. Subfossil representatives of Hystricella bicarinata are not known. Seddon (2008: 181) depicts the distribution of H. bicarinata. The four southernmost points indicate the presence of the species also for the southern ridge of eastern Porto Santo. We here infer that these localities are based upon misidentifications with other species, probably some representatives of Wollastonia, i.e., W. jessicae sp. n. or W. klausgrohi sp. n.

Figure 54. 

Distribution of Hystricella bicarinata.

Hystricella bicarinata is commonly found under volcanic rocks scattered on grassland in open fields that are more or less sloping. It has also been found under stones in pine woods (Pico do Castelo) or in cracks and crevices on rocky walls (Pico da Gandaia) or terraced areas (southern slopes of Pico do Castelo). The specimens aestivate on the lower surfaces of stones or rocks, frequently forming large clusters of 40 to 50 individuals attached one to another. Under a single stone of roughly 60 × 40 cm approximately 200 individuals were observed (southern slopes of Pico do Facho).

The presence of two keels along the body whorl easily distinguishes H. bicarinata from H. echinulata. Where both taxa come into contact in the northern to northeastern part of Porto Santo (Fig. 4) intermediate populations exist however, suggesting a possible hybrid zone (see below).

At first glance, and due to the small dimensions, H. bicarinata can be confused with the fossil species H. aucta and H. microcarinata sp. n. (see Fig. 74). However, a closer analysis reveals major differences in many features of the shell. Hystricella aucta has a more solid shell with two, almost equally developed keels along the body whorl. The penultimate and the third whorl have a single strong upper keel only. The tubercles in H. aucta are much smaller and finer than in H. bicarinata (see Figs 71–73).

Hystricella microcarinata sp. n. resembles H. bicarinata with regard to dimensions and overall shape; however, the weak keels along the penultimate and body whorl and the well-developed and rather elevated growth lines allow the separation of the two species. Moreover, the tubercles in H. microcarinata sp. n. are somewhat smaller and more scattered.

Hystricella bicarinata can also resemble some of the species included in the newly described genus Wollastonia gen. n. Species such as W. turricula, W. leackociana and W. oxytropis differ in the very fine granulation present on the shell’s surface. These species do not possess evident tubercles but only small granules that are remarkably smaller in dimension than the tubercles of H. bicarinata. Moreover, the overall shape of all three above-mentioned species is different from that of H. bicarinata (see e.g. Figs 100, 119, 130). Other (sub-) species assigned to Wollastonia gen. n. such as W. vermetiformis, W. jessicae jessicae sp. n., W. jessicae monticola ssp. n., and W. klausgrohi sp. n. (see Figs 118–120, 147–149, 159–161, 168–170) are somewhat similar to and could be confused with H. bicarinata. These taxa can be readily distinguished, however, by their more scalariform shape, somewhat stronger keels, and the sparser arrangement of the tubercles. Moreover, the distributional ranges of Hystricella and Wollastonia gen. n. do not significantly overlap and molecular data strongly supports differentiation at the genus-level (thus also at species level).

We report below a statement sent to us by Ruud Bank referring to the erroneously introduced name Helix duplicata R. T. Lowe, 1831. “The name Helix [Cochlitoma] bicarinata A. Férussac, 1821 does not exist! Férussac simply reclassified Bulimus bicarinatus Bruguière, 1792 under Helix (Cochlitoma). Thus, Helix bicarinata G. B. Sowerby I, 1824 was at that time (and only for a very short period of time) a secondary homonym of Helix bicarinata (Bruguière, 1792). Helix duplicata R. T. Lowe, 1831 was introduced to replace the name of Sowerby due to homonymy with the Férussac name, but as stated above, Férussac did not introduce such a name, it was simply a generic change for Bulimus bicarinatus Bruguière. In my opinion, the name duplicata cannot be considered a nomen novum. It would have been only a nomen novum when R. T. Lowe mentioned Bruguière as the author of the senior taxon – what he didn’t.

Mandahl-Barth (1950), Jaeckel (1966) and Waldén (1983) placed this taxon in Discula and considered Hystricella as a subgenus. Bank et al. (2002) considered the species to belong to a distinct genus (under the name Geomitra). Only recently Seddon (2008) appointed this species to the genus Hystricella and emphasised anatomical differences with the genus Discula.

The opinion of Seddon (2011a) “[Hystricella bicarinata] has a total extent of occurrence of 10 km² but is present over the eastern part of the island and in these sites it is abundant” has been confirmed by our field researches. For this reason, we think that the assessment as Near Threatened (NT) is appropriate at present.

1867 Helix (Octephila) vermetiformis var. α minor Paiva: 48 [non Helix minor mult. auct.].

1878 Helix (Hystricella) bicarinata var. ß aucta Wollaston: 162–163.

1950 Discula (Hystricella) bicarinata aucta – Mandahl-Barth: 31, 55.

1983 Discula (Hystricella) bicarinata aucta – Waldén: 267.

2002 Geomitra bicarinata aucta – Bank et al.: 124.

2006 Discula bicarinata aucta – Cameron et al.: 31.

2008 Hystricella bicarinata aucta – Seddon: 79.

2009 Hystricella bicarinata aucta – Groh et al.: 21 fig. 25.

Despite intensive research in multiple museum collections (NHM, NMW, MMUE, ANSP, NHC, NMS, RAM, SMF) that could have held the type material of the taxon, no such material could be traced and therefore we deem it reasonable to assume that the type material is lost. To stabilise the present interpretation of Helix (Hystricella) bicarinata var. ß aucta Wollaston, 1878 and to clarify its taxonomic status we designate a neotype here, which is deposited in the collection of the SMF, under the No. SMF 348937 (see Fig. 71). The neotype is consistent with the original description (see below), especially with regard to size, shape and the presence and development of the two keels on the body whorl. The taxon was originally described from Porto Santo, which is consistent with the origin of the specimen selected as neotype.

Figures 71–74. 

Shells of Hystricella aucta. 71 neotype, SMF 348937 from Barbinha 72 Barbinha 73 Ponta da Canaveira 74 Hystricella microcarinata sp. n., holotype, SMF 348924. Scale bar: 1 mm.

[aucta] Barbinha, Quaternary slope deposits, "grey layer", 33°04'04"N/16°17'49"W, 8 m, (through the designation of the neotype); [var. minor]: … rara ad Zimbral d'Aréa.

All from Porto Santo, CKG/1, S slope of Pico do Concelho, Quaternary slope deposit, 33°04'35"N/16°18'03"W, 200–230 m, leg. K. & C. Groh, Jun. 29 1980; CKG/2, Barbinha, Quaternary slope deposits, "grey layer", 33°04'04"N/16°17'49"W, 8 m, leg. K. & C. Groh & J. & C. Hemmen, Jul. 4 1983; ANSP H 11789/9 [sub H. bicarinata], Barbinha, Quaternary slope deposits, "red layer", 33°04'04"N/16°17'49"W, 8 m, leg. J. Gerber, K. Groh & J. Hemmen, Aug. 12 1985. CKG/1, first bay S of Barbinha, Quaternary slope deposit, 33°03'51"N/16°17'46"W, 18 m, leg. K. & C. Groh & J. & C. Hemmen, Jul. 5 1983. CGK/3, Ponta da Canaveira, Quaternary aeolinites, 33°02'30"N/16°23'35"W, 50 m, Jun. 24 1983, leg. K. Groh & J. Hemmen; CGK/3, S of Ponta da Canaveira, Quaternary aeolinites, 33°02'30"N 16°23'34"W, 55 m, Oct. 26 1980, leg. K. Groh & J. Hemmen; CKG/2, Vale do Touro, Quaternary slope deposit cut by water erosion in the banks of the valley, 33°03'48"N/16°19'17"W, 15 m, leg. K. & C. Groh, Aug. 16 1980; CWDM/14, S slope of Vale do Touro hill, 50 m W of the oil tanks, fossils beds in mixed gravel and mud deposits, 33°03'47"N/16°19'26"W, 15 m, leg. W. De Mattia & J. Macor, May 2015; CFW 12172/1 fragm. [cf. aucta], Ponta da Galé, E end of tunnel, lower level [of slope deposits], coarse, red coloured gravel with large stones, 33°03'44"N/16°17'45"W, 30 m, leg. F. Walther, Apr. 4 2017; CFW 12173/16, CKG/3, S of Ponta da Canaveira, (sub-)fossil [slope-]deposits, coarse, red coloured gravel, 33°02'25"N/16°23'41"W, 30 m, leg. F. Walther, Apr. 2 2017; CFW 12175/8, E of Vila Baleira, end of Vale do Touro, (sub-)fossil [slope-] deposits, coarse, black gravel, 33°03'48"N/16°19'15"W, 20 m, leg. F. Walther, Apr. 5 2017; CFW 12174/13, CKG/2, E of Vila Baleira, S slope of the hill above Vale do Touro, W of the oil tanks, [(sub-)fossil slope-deposits of] red gravel, 33°03'47"N/16°19'26"W, 25 m, leg. F. Walther, Apr. 5 2017.

[aucta]: From Wollaston 1878: There is however an appreciably larger form of this species [bicarinata] (cited in the present catalogue as the 'var. ß. Aucta’) to which the subfossil examples might perhaps be better referred, – in which the upper (or medial) keel is a trifle more horizontal and prominent, and the shell is full 3 lines (instead of only approximately 2½) across its broadest part – which was found in Porto Santo by Mr. Watson, and which I have received from him as the 'recent state of the H. vermetiformis, Lowe.' the 'var. ß. Aucta' of the H. bicarinata in its very much larger size, and in its volutions (the ultimate one of which is not quite so deflected at the aperture) being 7 in number, instead of only 6 or 6½; [var. minor]: From Paiva 1867: Variet. adest α minor, testa minore.

Shell small for the genus, with 5.7 regularly increasing whorls, the protoconch with 1.9 whorls. The form of the shell is conical, the concave teleoconch whorls, with two prominent keels situated at the upper ⅐, respectively ⅖ of the total height of the last whorl. The last whorl measures 62%, the penultimate whorl 19% of the total shell height. The lower 60% of the body whorl beneath the second keel are rather straight, only a little convex in the middle. The suture is simple, only slightly sunken beneath the second keel of the preceding whorl. The aperture, which is inclined to the vertical axis of the shell in an angle of 49° and is descending in the last 5% of the last whorl in an angle of 38° to the horizontal axis, has an elliptical-ovate form, its width is 42% of the total shell width and its height 27% of the total shell height. It has an only slightly reflected lip, which is completely detached from the body whorl. The eccentric umbilicus, which is approximately 12% as wide as the shell, is in the upper whorls needle stitch-like. The protoconch is smooth. The teleoconch is equipped with few oblique radial ribs, seven in the penultimate quadrant of the body whorl and is additionally covered by numerous coarse tubercles. The number of tubercles in the standard quadrate of the base is 31; the tubercles are of approximately equal size. There are no traces of colouration (Figs 71–73).

D 5.5 ± 0.5 mm (range 5.1–6.4 mm); H 4.6 ± 0.4 mm (range 4.1–5.3 mm); FW 2.8 ± 0.2 mm; PA 51 ± 2.1; DU 0.5 ± 0.03 mm; NT 18 ± 6; NW 5.5 ± 0.4 (n = 22). Ratio D/H 1.2; ratio FW/H 0.6.

Hystricella aucta is known only from the southeastern coast of Porto Santo: from the hill immediately east of Vila Baleira (mud and slope deposits at Vale do Touro) to the mud deposits and aeolinites along the southeastern coast (Barbinha, Zimbral da Areia, and Porto dos Frades) (Fig. 75).

Figure 75. 

Distribution of Hystricella aucta.

Because of its small size, the species can only be confused with the similar sized recent H. bicarinata which, however, is somewhat larger on average, has less developed keels, especially the upper one is less prominent and has coarser and denser tubercles on its shell surface, a narrower umbilicus and a more distinctly descending aperture. The smaller H. microcarinata sp. n., which has a much more rounded globular form, bears less prominent keels on the whorls, has finer and more densely arranged tubercles, has a much narrower umbilicus and a different shape as well as differently positioned angles of the aperture. The similar sized Wollastonia beckmanni sp. n., which has a much flatter shape, has no keels on the whorls, a much wider umbilicus, much more and finer tubercles and differently positioned angles of the aperture.

Considered by Wollaston (1878) as the fossil variation of H. bicarinata. We here consider it as a distinct species because of the shell differences. Like H. bicarinata, H. aucta has previously (Mandahl-Barth 1950, Waldén 1983, Bank et al. 2002) been listed as belonging to Discula and later on to Geomitra.

Extinct before the islands’ scientific exploration in the 19^th century, possibly already before human settlement.

SMF 348924, holotype, from loc. typ. (locus typicus), leg. W. De Mattia & J. Macor, May 2016.

Porto Santo, E of Vila Baleira, S slope of the hill above Vale do Touro, 50 m W of the oil tanks, excavated Quaternary mixed gravel, 33°03'47"N/16°19'26"W, 24 m.

Hystricella species with two keels on the body whorl, the upper less developed than the lower one; growth lines rather coarse, giving the impression of an irregular ribbing; tubercles on the base of the shell rather scattered and not as prominent as in H. bicarinata.

Shell very small for the genus, with 5⅓ regularly increasing whorls, the protoconch with 1.6 whorls. The form of the shell is rounded conical, the convex teleoconch whorls exhibit two flat keels that become more and more expressed; the upper keel is much less developed than the lower one; keels on the body whorl located in its upper half. The last whorl measures 69%, the penultimate whorl 15% of the total shell height. The lower half of the body whorl is, beneath the distinctly angled periphery, in frontal view nearly straight, only very slightly convex. The suture between the whorls is simple, not sunken. The aperture, which is inclined to the vertical axis of the shell in an angle of 50° and is descending in the last 5% of the last whorl in an angle of 36° to the horizontal axis, has an oblique-ovate form, its width is 43% of the shell width, its height 34% of the shell height. It has a slightly reflected lip, which is completely detached from the body whorl. The eccentric umbilicus, which is approximately 11% as wide as the shell, is shaped in the upper whorls like a pinhole. The protoconch is smooth. The teleoconch exhibits a number of oblique radial ribs, 16 in the penultimate quadrant of the body whorl and is additionally covered by numerous rough tubercles. The number of tubercles in the standard-quadrate of the base is 43. There are no traces of colouration (Fig. 74).

D 4.1; H 4.2 mm; FW 2.7 mm; PA 49°; DU 0.3 mm; NT 12; NW 4.8 (n = 1). Ratio D/H 0.9; ratio FW/H 0.6.

The species is only known from the type locality where it appears to be extremely rare (Fig. 76). Its close resemblance to other (sub-) fossil Hystricella taxa may have led to misidentifications during previous collecting and sorting, thus the distribution area of the species may possibly become larger after further investigations.

Figure 76. 

Distribution of Hystricella microcarinata sp. n.

The name is a combination of the Greek name for small (μικρός = mikrós) and the Latin name for keeled (carinatus) and alludes to the small size of the shell with a keel at its periphery.

Being a (sub-) fossil species, only the shell features can be taken into account for comparisons. The globose shape is similar to that of some forms of H. echinulata; nevertheless the overall dimensions and surface sculpture of the shell clearly distinguish H. microcarinata sp. n. Because of its small size, the new species can also be confused with small specimens of H. aucta Wollaston, 1878 which, however, possesses two well-developed keels, has a wider umbilicus, a different shape and differently positioned angles of the aperture, or with Wollastonia beckmanni gen. et sp. n., which has a much flatter spire, has no keels on the whorls, a much wider umbilicus and also a different shape and differently positioned angles of the aperture.

The generic affiliation of this species is based exclusively on the shape of the shell and the presence of keels on the body whorl. A similar arrangement of the tubercles and keels can be found also in some Wollastonia gen. n. species that will be described below.

Extinct before the islands’ scientific exploration in the 19^th century, possibly already before human settlement.

1831 Helix echinulata R. T. Lowe: 57, pl. 6 fig. 19.

1846 Helix echinulata – L. Pfeiffer: 140, pl. 91 figs 1–4.

1847 Helix echinulata – L. Pfeiffer in L. Pfeiffer 1847–1848: 190.

1854 Helix echinulata – Reeve in Reeve 1851–1854: pl. 142 figs 9–10.

1854 Helix echinulata – Albers: 36, pl. 9 figs 1–4.

1855 Helix (Hystricella) echinulata – R. T. Lowe: 186.

1867 Helix (Octephila) bicarinata var. α echinulata – Paiva: 45.

1878 Helix (Hystricella) echinulata – Wollaston: 160–161.

1950 Discula (Hystricella) echinulata – Mandahl-Barth: 31, 55.

1983 Discula (Hystricella) echinulata – Waldén: 267.

2002 Geomitra echinulata – Bank et al.: 124.

2008 Hystricella echinulata – Seddon: 79, pl. 29 fig. D (and cf. E [under H. bicarinata]), map 178.

2011 Hystricella echinulata – Seddon: e.T6727A12801253.

NHM 1968.586, lectotype (herewith designated) of Helix echinulata R. T. Lowe, 1831 ex coll. R. T. Lowe. For the original figure of Helix echinulata R. T. Lowe, 1831 from R. T. Lowe (1831: pl. 6 fig. 19) and the lectotype of H. echinulata R. T. Lowe, 1831, W = 4.9 mm, Phot. B. Faria, DRAM, see Figs 77 and 78.

Figures 77–78. 

77 original figure of Helix echinulata R. T. Lowe, 1831 from R. T. Lowe (1831: pl. 6 fig. 19) and 78 lectotype of Helix echinulata R. T. Lowe, 1831, NMH 1968.586 ex coll. R. T. Lowe. Scale bar: 1 mm.

All from Porto Santo, ANSP H 11829/1, Ribeiro do Pedregal, 33°06'10"N/16°19'25"W, 35 m, leg. K. Groh & J. Hemmen, Jul. 11 1983; ANSP H 11828/16, CKG/5, Pico do Ninho do Guincho, 33°06'07"N/16°18'51"W, 100 m, leg. K. Groh & J. Hemmen, Jul. 11 1983; CKG/1, Ribeiro do Golfeiras E Camacha, 33°05'47"N/16°19'33"W, 170 m, leg. K. & C. Groh, Oct. 25 1980; ANSP H 11831/3, CKG/1, CMN/1, SW slope of Lombo Branco, under stones, 33°05'46"N/16°18'46"W to 33°05'38"N/16°18'13"W, 150–400 m, leg. K. Groh & J. Hemmen, Jul. 8 1983; ANSP H 11830/4, Terra Chã, top, 33°05'46"N/16°18'14"W, 360 m, leg. J. Gerber, K. Groh & J. Hemmen, Aug. 14 1985; CFW 11162/5, Pico Branco, Terra Chã (350 m E of Pico Branco), 33°05'39"N/16°17'58"W, 340 m, leg. F. Walther, Mar. 31 2017; CWDM/19, CMN/5, Terra Chã, near the "Casa Forestal", under stones in pine wood. 33°05"39"N/16°20'00"W, 340 m, leg. W. De Mattia & J. Macor, May 2014; CWDM/6, Terra Chã-Pico Branco ridge, under stones, 33°05'38"N/16°18'01"W, 335 m, leg. W. De Mattia & J. Macor, May 2015; ANSP H 11833/3, summit of Pico Branco, 33°05'38"N/16°18'14"W, 450 m, leg. K. Groh & J. Hemmen, Jul. 8 1983; ANSP H 11836/15 [sub H. leacockiana], Pico Branco, 33°05'38"N/16°18'14"W, above 350 m, leg. J. Gerber, K. Groh & J. Hemmen, Aug. 14 1985; CKG/16, Terra Chã, top, 33°05'36"N/16°18'14"W, 360 m, leg. J. Gerber, K. Groh & J. Hemmen, Aug. 14 1985; CKG/2, Terra Chã, 33°05'31"N/16°18'16"W to 33°05'38"N/16°18'13"W, 320–400 m, leg. K. Groh & J. Hemmen, Jul. 8 1983; CWDM/14, path to Pico Branco, eastern steep part of path to Pico Branco, under stones, 33°05'29"N/16°18'14"W, 320 m, leg. W. De Mattia & J. Macor, May 2014; CFW 11148/<10, SW slope of Pico Branco ca. 250 m SW of the top, 33°05'29"N/16°18'13"W, 310 m, leg. F. Walther & E. M. Gryl, Mar. 31 2017; ANSP H 11826/7, approx. 1 km N Serra de Dentro, 33°05'24"N/16°18'27"W, 165 m, leg. J. & C. Hemmen, Jan. 6 1981; ZMH 24292/1, Madeira Archipelago, without exact locality data, ex coll. Altonaer Museum, ex coll. O. Semper, ex coll. Dohrn; ZMH 24291/1, Porto Santo, without exact locality data, ex coll. Museum Klagenfurt.

Hab. in monte “Pico Branco” dicto Insulae Portus S^ti.

From Lowe 1831: H. testa parvula, conoidea, sub-pyramidata, depressiuscula, supra planulata, perforata, carinata, tota scaberrima, fusca, suprà fasciata: spira pyramidata elevata; sutura distincta, impressa; anfractibus convexis; ultimi carina acuta, distincta, supra marginata sc. sulco expressa vel exarata; omnibus granulis distinctissimis, conferitis, asperrimis scobinatis et quasi echinulatis; umbilicus parvo, sub-spirali, aperto; apertura rotundata; peristomate continuo, circinato, disjuncto, reflexo. Axis 2 lin. Diam. 2½. Anfr. 6.

Shell as in the genus description. The main diagnostic feature is the presence of only one keel along the body whorl. The overall shape of the shell of H. echinulata is always conical but not scalariform as in H. bicarinata. The whorls are rounded and lack the typical “shoulder”. The sutures are deep, but less deeply marked than in H. bicarinata (see Figs 79–82).

Figures 79–82. 

Shells of Hystricella echinulata. 79–80 Terra Chã 81 S slope of Pico Banco 82 steep path from Pico Branco to Terra Chã. Scale bar 1 mm.

D 5.2 ± 0.3 mm (range 4.6–5.8 mm); H 4.8 ± 0.5 mm (range 4.3–5.0 mm); FW 2.5 ± 0.2 mm; PA 42.6 ± 8.3; DU 0.5 ± 0.08 mm; NT 23 ± 9; NW 5.6 ± 0.1 (n = 40). Ratio D/H 1.1; ratio FW/H 0.5.

Body as in the genus description. The colour of the head and the neck is somewhat darker than in H. bicarinata.

As in the genus description. Main diagnostic features are as follows. The free oviduct is usually very short and four times shorter than the vagina. The penial flagellum is usually as long as the epiphallus. It has a remarkably cylindrical shape and a blunt apex. Its internal walls are completely smooth, without any papillae. The genital atrium is always elongated. See Figs 83–93.

Figures 83–93. 

Anatomy and genitalia of Hystricella echinulata. Terra Chã: 83 whole genitalia excluding gonads 84 ornamentation of the inner walls of the distal penis, the distal vagina and the genital atrium 85 ornamentation of the inner walls of the flagellum, the penial complex, the vagina and the genital atrium 86 penial papilla 87 whole genitalia excluding part of OSD, AG and gonads 89 penial papilla and ornamentation of the inner walls of the flagellum 91 mantle border 92 section of penial papilla. Faja Pequena: 88 section of vagina 90 jaw 93 whole genitalia excluding gonads. Scale bars 1 mm.

Hystricella echinulata is recorded from low (20 m a.s.l.) to relatively high altitudes (450 m a.s.l.). Except for the slightly higher altitudinal range, this species shares the same ecology as H. bicarinata; it is commonly found under volcanic rocks scattered on grassland in open fields that are usually sloping. It has also been found in cracks and crevices or among scree on steep slopes.

Hystricella echinulata is endemic to the island of Porto Santo (Madeiran Archipelago, Portugal). The species is restricted to the northeastern, mountainous part of the island and present only in the Pico Branco-Terra Chã massif area. It is commonly found along Faja Pequena and the ridge and the south-exposed slope eastwards of Terra Chã (Fig. 94). No populations are known from the offshore islets.

Figure 94. 

Distribution of Hystricella echinulata.

See under H. bicarinata and/or the section on putative hybrids of H. bicarinata and H. echinulata above.

According to Seddon (2011b) the species is Least Concern (LC), but in our opinion, the species should be considered as Endangered (EN B1a, b(i, ii, iv), 2a, b(i, ii, iv)) because its area of occupancy and extent of occurrence is less than 8 km² and because it is mostly restricted to the highest elevations in the north-eastern part of Porto Santo and only occurs at scattered and isolated places with suitably humid microclimates. Mayor threats to the species include an observed decline of suitable habitats, extent of occurrence and area of occupancy over the past 30 years, i.e. as the result of longer drought periods which are possibly associated with effects of climate change, an increase of fire incidents, grazing by goats and to a lesser extent also hiking as tourism is increasing on Porto Santo. As most of the known localities are concentrated in the Pico Branco-Terra Chã area in the north-easternmost part of Porto Santo (Fig. 94), we consider that the species is not present at more than five locations.

1878 Helix (Hystricella) echinoderma Wollaston: 159–160.

1894 Geomitra echinoderma – Pilsbry in Pilsbry 1893–1895: 242.

1931 Geomitra (Actinella) echinoderma – Nobre: 88.

1950 Discula (Hystricella) echinoderma – Mandahl-Barth 1950: 31, 55.

1983 Discula (Hystricella) echinoderma – Waldén: 267.

2002 Geomitra echinoderma – Bank et al.: 124.

2008 Hystricella echinoderma – Seddon: 80.

NHM 1875.02.02-52, lectotype (herewith designated) from loc. typ.; NHM 1875.02.02-53 to -54, 2 paralectotypes, from loc. typ.

Portum Sanctum, semifossilis; recens haud observata.

From Wollaston 1878: T. trochiformis, subtus subplanulata perforata, undiquegranulis magnis obtusis sat dense obsita; spira elevata; anfractibus convexis, subgibbosis, ultimo subtectiformi acute carinato (carina simplici, solum antice gradatim obsolete subduplici); umbilico punctiformi, aperto; apertura subovali-rotundata, labris continuis conjunctis, peristomate simplici, expanso, subrecurvo, tenui, relevato. – Long. axis 2 ½ lin.; diam. 3 ½.

Shell large for the genus, with 6¾ regularly increasing whorls, the protoconch with 1.9 whorls. The form of the shell is high conical, the convex to quadrangular teleoconch whorls showing two more and more expressed angulations which form in the last whorl two rounded keels, the upper less developed than the lower one. The last whorl measures 59%, the penultimate whorl 14% of the total shell height. The lower 70% of the body whorl are situated below the peripheral keel which is slightly constricted by a concavity below the periphery in frontal view. The base is convex, slightly straightening towards the umbilicus. The two keels of the body whorl are located in the upper ⅛ and ⅓ of the total height of the body whorl. The suture between the whorls is simple but deeply sunken. The aperture, which is inclined to the vertical axis of the shell in an angle of 48° and descending in the last 5% of the last whorl in an angle of 38° to the horizontal axis, has an oblique-ovate form, its width amounts to 43% of the total shell width, its height to 34% of the total shell height. It has a slightly reflected lip, which is completely detached from the body whorl. The centered umbilicus, which measures 10% of the shell’s total width, is in the last whorls circular, but completely closed deeper inside. The protoconch is smooth, the teleoconch shows a number of oblique radial ribs, 15 in the penultimate quadrant of the body whorl, and is additionally covered by numerous irregularly arranged, elongate, rough tubercles. The number of tubercles in the standard-quadrate of the base is 81. There are no traces of colouration. See Fig. 95.

Figure 95. 

Lectotype of Hystricella echinoderma, NHM 1875.02.02-52. Scale bar 1 mm.

D 7.0 mm; H 5.9 mm; FW 3.5 mm; PA 42.2°; DU 0.5 mm; NT ≈ 35; NW 6.6 (n = 1). Ratio D/H 1.2; ratio FW/H 0.5.

Hystricella echinoderma is only known from Fonte da Areia in the northern part of Porto Santo (Fig. 96).

Figure 96. 

Distribution of Hystricella echinoderma.

Hystricella echinoderma can be confused on first glance with comparatively large-sized species of the genus Wollastonia like W. vermetiformis, W. ripkeni sp. n., and W. falknerorum sp. n.; from these it is distinguishable by the lack of one or two sharply pointed keels, respectively, a much rougher sculpture, a non-eccentric umbilicus, and the stepped, high conical form. From the similarly sized W. subcarinulata and W. inexpectata sp. n. it is separated by a wider or non-eccentric umbilicus, a relatively higher shell, the quadrangular instead of convex rounded whorls, a coarser granulation and the oblique-ovate instead of straight horizontally elliptical aperture. From the similar shaped H. echinulata and H. microcarinata sp. n. it is easily distinguishable by the much larger size.

Wollaston (1878) compares H. echinoderma with the rather similar H. echinulata and calls it a monstrous sister species of that species, citing as examples of pairs of nominal species with a distinct size difference Helix vermetiformis and H. bicarinata, H. Lowei and H. portosanctana as well as H. bowdichiana and H. punctulata.

Extinct before the islands’ scientific exploration in the 19^th century, possibly already before human settlement.

The synonymy is the same as for the genus Hystricella (see above).

Helix [Helicella] turricula R. T. Lowe, 1831 – herewith by original designation.

Wollastonia turricula (R. T. Lowe, 1831), comb. n., W. vermetiformis (R. T. Lowe, 1855), comb. n., W. ripkeni De Mattia & Groh, sp. n., W. falknerorum Groh, Neiber & De Mattia, sp. n., W. leacockiana (Wollaston, 1878), comb. n., W. beckmanni De Mattia & Groh, sp. n., W. jessicae jessicae De Mattia, Neiber & Groh, sp. n., W. jessicae monticola De Mattia, Neiber & Groh, ssp. n., W. klausgrohi De Mattia & Neiber, sp. n., W. oxytropis (R. T. Lowe, 1831), comb. n., W. subcarinulata (Wollaston, 1878), comb. n., W. inexpectata De Mattia & Groh, sp. n.

Shell. The shell is dextral and hairless. Its shape can be very variable, from conical, elongated and scalariform with deep sutures to rather flattened, with very shallow sutures. The protoconch is from whitish to completely dark brown with 1.5 to 2.5 whorls. It is almost smooth along the first whorl and shows fine radial striae and extremely small, scattered tubercles along its remaining portion. The teleoconch has from 4.3 to 7.0 rapidly increasing whorls. It is usually dark brown with brick-red and/or dark violet shades in colour. The dark areas of the shells are mottled with more or less light brown to whitish areas, usually placed longitudinally and slightly slanting. In some species, the lighter areas tend to be more evident along the keel. No band pattern is visible along the upper whorls. On the lower part of the last whorl two dark, more or less broad bands may be present. In some specimens, the two bands merge together forming a single wide, dark band. Sometimes the bands are interrupted by yellowish to whitish sections. The area around the umbilicus is usually the lightest in colour. Some species are usually covered entirely with soil or sand grains which probably serve as a camouflage.

The spire is very variable in height, ranging from flattened, almost discoidal to slender and remarkably conical in shape. The number and the extent of the keels are variable from species to species. Some species have one or two distinct keels starting already from the second whorl of the teleoconch, while others have a single, more or less strong keel only along the last whorl. Some species have a lower, distinct principal keel somewhat protruding the body whorl, with an upper secondary and much less evident keel. The whorls can be either convex or flat. In some species, the whorls form a “shoulder”, giving the whorls and angular contour. The sutures are usually deep, even if in some species they may also be rather shallow.

The external surface has from very fine to strong, clearly visible, irregularly spaced, growth lines. Irregularly disposed tubercles are found all over the teleoconch. The dimensions and the arrangement of these tubercles varies considerably from species to species, from large and scattered tubercles to a very dense pattern of small papilla-like tubercles all over the shell. In the species with larger tubercles, these are somewhat denser along the keels of the penultimate and last whorls, giving to the keel(s) the appearance of (a) rough chord(s). The last whorl is usually large, descending near the aperture with a contribution ranging from 40% to 60% of the total shell height. The umbilicus is open but very narrow, either concentric or eccentric, and measures approximately 10% of the maximum shell diameter. The aperture is elliptical with a faint thickening along the columellar portion of the aperture. Sometimes this thickening can also extend as far the parietal side of the aperture. The peristome is continuous, slightly to evidently reflected, with the columellar margin somewhat thicker and more reflected.

The shells of the species belonging to Wollastonia gen. n. show a remarkable plasticity, with regard to dimensions, shape and ornamentation. This variability undoubtedly exceeds that of the genus Hystricella. Thus, for each taxon, the shell’s features will be described in detail.

Body. The head and neck are usually dark grey to grey. The sides and the posterior upper section of the foot are whitish. In some species, the pigmented ommatophoral retractor muscles are visible through the skin of the back of the cephalic area. The foot is white and the sole is longitudinally divided into three areas. The central area is smooth, whereas the two lateral areas are equipped with bands of muscles roughly arranged in a chevron pattern. The mantle border is grey to dark grey with five more or less developed lobes. The ratio of lateral to the dorsal lobes varies from specimen to specimen, also in the same population. In some specimens one of these lobes (either lateral or dorsal) may be totally missing. The walls of the pallial cavity are colourless, without any stripes or spots. A strong pulmonary vein is visible. The jaw is odontognathous and very variable in shape, from almost straight to markedly arched. There are many transversal, smooth ridges, ranging from eight to 25 in number. The right ommatophoral retractor is independent from both penis and vagina.

Genitalia. The general arrangement of the genitalia is semi-diaulic monotrematic. A convoluted to almost straight hermaphroditic duct arises from a multi-lobated gonad. The albumen gland is long and thin and connected to a variably long sperm-oviduct consisting of a prostatic and a uterine portion. The prostatic part extends into a thin vas deferens, roughly as long as the sperm-oviduct, and terminating in the penial complex. The distal portion of the uterine part extends into the free oviduct and turns into a vagina along its course at the level of the duct of the bursa copulatrix. The free oviduct can be as long as the vagina or also three to four times longer. The duct of the bursa copulatrix is usually wide, approximately as long as the penis and uniform in diameter. It extends into a variable, oval to roundish bursa copulatrix. In some species, the transition area between the duct and the bursa itself is not very distinctly delimited; the duct more or less abruptly widens and transforms into the bursa. The spermatophore is unknown. One tuft of digitiform glands arises from the proximal part of the vagina. The glands have usually two or three, approximately equally long and very rarely bifurcated branches. A short and thin vaginal appendix arises from the vagina’s wall, immediately distal of the glandular tuft. Very smooth, rather wide, and little elevated, irregularly spaced pleats run longitudinally along the inner surface of the vagina, reaching into the genital atrium as far as the genital orifice. The atrium can be short and wide or long and thin. Its internal walls can either be smooth or with large and soft pleats running longitudinally as far the genital orifice. The penial complex consists of a flagellum, an epiphallus (which extends from the insertion of the vas deferens to the penial retractor muscle) and a penis that inserts into the atrium. The penial flagellum is short, remarkably cylindrical and with a blunt apex. It is usually as long as the epiphallus. In one species, W. oxytropis, the flagellum is very short (¼ of the epiphallus) but remarkably pointed. The internal walls of the flagellum can be either completely smooth or, in one species, can have a digitiform, pointed papilla originating from the proximal end of the flagellum and orientated toward the penial papilla. The epiphallus is usually short to moderately long. Its internal walls have a variable number of longitudinal pleats that can be more or less developed and elevated. The retractor muscle is large, strong and is of a variable length. The penis lacks a muscular or glandular sheath. It is thick-walled and approximately four times longer than the flagellum. It is usually cylindrical to sometimes slightly swollen in its distal part. Sometimes, a thin sheath consisting of connective tissue envelops the distal penis, causing a partial and longitudinal minor compression. The inner walls of the penis are smooth or with irregular and spaced pleats, which run longitudinally and reach the genital atrium. The section where the penial papilla is located is usually detectable from the outside by virtue of a fine circular swelling corresponding to the origin of the papilla. The penial papilla is usually small, reaching maximally ⅛ of the total penial length and is conical to subcylindrical in shape. It has smooth external walls with the opening emerging apically. The penial papilla channel is thin and narrow. The inner lumen of the penial papilla is occupied by a spongy and sturdy tissue, which directly connects with the walls of the epiphallus. The longitudinal section of the penial papilla shows that its walls are the continuation of the penial walls that abruptly bend inwards.

Jaw and radula. As for the genus Hystricella, no notable variability was found among the species of the genus Wollastonia gen. n. and the two genera share almost an identical jaw-radular apparatus. The jaw is odontognathous, arched and with rough wrinkles (irregular ribs). The radula ribbon is typical helicoid, it is elongated but not very slender. A central tooth is present, tricuspid, the main cusp (endocone) is rhomboid, pointed; the ectocones are much smaller than the endocone, they are triangular, pointed. There are 19–20 laterals and marginals, which do not distinctly differ from each other. Their shapes rather change gradually from the first laterals towards the marginals. Laterals are bicuspid, with rhomboid or triangular and pointed endocones. The ectocones are much smaller, pointed, and triangular. The endocones of the central and first laterals are approximately of the same size. Both the endocone and the ectocone of the laterals gradually become bifurcated towards the marginal teeth, but the ectocones occasionally might have three cusps as well. The cusps of the marginals are gradually decreasing in size; therefore, the outermost marginals appear serrated. The jaw is variable in shape: from almost straight to markedly arched. There are many transversal and smooth ridges, ranging from 13 to 20. For Wollastonia jaws and radulae, see Fig. 98.

The genus Wollastonia is endemic to the island of Porto Santo (Madeiran Archipelago, Portugal) and some surrounding islets (Fig. 97). Along the eastern part of the main island, the genus is restricted to the southern mountainous part. It is patchily distributed from the hilly area east of Vila Baleira towards the east to Portela, Zimbreiro and along the highest southern peaks of Porto Santo, namely Pico do Maçarico and Pico do Baixo as far as Ponta da Galé. It is also present along the eastern coast area of Pico do Concelho. Along the western part of Porto Santo, Wollastonia is found on Pico de Ana Ferreira. With regard to the surrounding offshore islet, Wollastonia is present on Ilhéu de Cima and Ilhéu de Cenouras at the eastern and Ilhéu de Ferro at the western end of the island. Subfossil representatives of the genus are found mainly in the mud and aeolinite deposits along the southeastern (Vale do Touro, Ponta do Passo, Barbinha, Calhau da Serra de Fora) and northern (Fonte da Areia) coasts. Wollastonia may be older than Hystricella as suggested by the somewhat deeper divergences in the molecular trees (Fig. 3).

Figure 97. 

Distribution of the genus Wollastonia gen. n. Filled circles refer to recent and open circles to fossil records.

Figure 98. 

Jaws and radulae Wollastonia gen. n. A W. leacockiana Pico de Ana Ferreira B W. oxytropis Pico do Concelho C W. jessicae jessicae sp. n. Vale do Touro.

Representatives of the genus Wollastonia are commonly found under volcanic rocks scattered on grassland in open fields and more or less steep mountain slopes. Specimens aestivate on the lower surfaces of the rocks, frequently forming clusters of individuals attached to one another.

Named to honour the late British malacologist and entomologist Thomas Vernon Wollaston for his indispensable contributions to the taxonomy and nomenclature of the terrestrial snails of the mid-Atlantic islands.

The genus Wollastonia gen. n. is separated here from Hystricella both upon molecular and morphological features. Moreover, the analysis of the distribution of its species supports this view.

The phylogenetic analyses recovered three clades, in which morphologically mostly similar species were grouped together and that were supported in at least two of the analyses. The clade including recent species hitherto assigned to Hystricella (except H. bicarinata and H. echinulata), supported in the BI and MP analyses (Figs 3, 5), are here regarded as representing a new genus, Wollastonia gen. n., because representatives of the morphologically distinct Callina species are interspersed between Wollastonia gen. n. and Hystricella in the strict sense receiving significant/meaningful support in the BI and MP analyses of the cox1 data alone and the concatenated mitochondrial and nuclear data. This clade includes the recent species W. leacockiana comb. n., W. turricula comb. n., and W. oxytropis comb. n. as well as three additional recent taxa that will be formally described below: W. klausgrohi sp. n., W. jessicae sp. n., and W. jessicae monticola ssp. n. (Fig. 5). The relationships of most of the taxa within Wollastonia gen. n. could, however, not be well resolved (Fig. 5) on the basis of the phylogenetic analyses of the cox1 data.

Shell size and shape are remarkably more variable in the genus Wollastonia as compared to Hystricella. Most of the Wollastonia gen. n. species have the shell surface covered with small and very dense tubercles that can be compared to a very fine granulation. The typical Hystricella’s “spiny” contour (Lat.: hystrix = spiny, deriving form Greek ὕστριξ (hústrix = porcupine) is replaced by a smoother one.

The genital morphology of the two genera shows no substantial differences. Nevertheless, some Wollastonia gen. n. species present a higher degree of complexity with regard to the inner ornamentation of the atrium and the flagellum. Structures such as more or less developed pleats, fleshy pads and/or fringes are found in Wollastonia gen. n. that are never present in Hystricella.

The distribution ranges of Hystricella and Wollastonia gen. n. are separated and not considerably overlapping. Wollastonia colonises the southern and southwestern parts of Porto Santo, whereas Hystricella is currently found exclusively in the central and northern parts.

Most of the morphological characters that clearly distinguish Hystricella from the other native Geomitridae of Porto Santo are also valid for Wollastonia. gen. n., e.g. the continuous and detached peristome and the shape of the penial flagellum that is always short and with a remarkably blunt apex (except in W. oxytropis stat. n.). For remarks on the differentiating features, see the respective section in the re-description of the genus Hystricella above.

1831 Helix turricula R. T. Lowe: 58, pl. 6 fig. 21.

1846 Helix turricula – L. Pfeiffer: 141, pl. 91 figs 5–7.

1847 Helix turricula – L. Pfeiffer in L. Pfeiffer 1847–1848: 190.

1854 Helix turricula – Reeve in Reeve 1851–1854: pl. 138 fig. 867.

1854 Helix (Ochthephila) turricula – Albers: 37, pl. 9 figs 11–13.

1855 Helix (Hystricella) turricula – R. T. Lowe: 186.

1867 Helix (Octephila) turricula – Paiva: 47.

1878 Helix (Hystricella) turricula – Wollaston: 163-165.

1878 Helix (Hystricella) turricula var. ß pererosa Wollaston: 165.

1888 Helix turricula – Tryon in Tryon and [Pilsbry] 1888: 33, pl. 7 fig. 91.

1894 Geomitra bicarinata – Pilsbry in Pilsbry 1893–1895: 242.

1923 Ochthephila turricula – Watson: 283–293, pl. 6 figs 1–10.

1931 Geomitra (Actinella) bicarnata – Nobre: 88, fig. 38.

1950 Discula (Hystricella) turricula – Mandahl-Barth: 31, 55.

1950 Discula (Hystricella) turricula pererosa – Mandahl-Barth: 31, 55.

1977 Discula (Hystricella) turricula – Pettitt: 147–150.

1983 Discula (Hystricella) turricula – Waldén: 267.

2002 Geomitra turricula – Bank et al.: 124.

2008 Hystricella turricula – Seddon: 79, pl. 29 fig. b, map 181.

2009 Hystricella turricula f. pererosa – Groh et al.: 21 fig. 28.

2011 Hystricella turricula – Seddon: e.T6723A12800477.

[turricula], NMH 1968.578, lectotype (herewith designated), from loc. typ., ex coll. R. T. Lowe; NMH 1948.7.8.35, 1 paralectotype, from loc. typ., ex coll. R. T. Lowe. The original figure of Helix turricula R. T. Lowe, 1831 (from Lowe 1831: pl. 6 fig. 21) is depicted in Fig. 99, the lectotype (Phot. P. Crabb, NHM) in Fig. 100; [pererosa], RAM EXEMS-1720-1909-d39-74a, lectotype (herewith designated), from loc. typ., ex coll. Linter, ex coll. T. V. Wollaston; RAM EXEMS-1720-1909-d39-74b, 1 paralectotype, from loc. typ., ex coll. Linter, ex coll. T. V. Wollaston (see Figs 113–115).

[turricula], Hab. in Insula quadam «Ilheo de Cima» dicta, juxta Insulam Portum S^tum; [pererosa], ‘Ilheo de Cima’.

All from Porto Santo. Fossil: CKG/10, CWDM/2, ZMH 116090/1 fragm [ex coll. E. Clauss], Quaternary slope deposits at the SW coast of the Ilhéu de Cima, 33°03'15"N/16°17'02"W, 40 m, leg. K. & C. Groh & J. & C. Hemmen, Jun. 26 1983 and leg. J. Gerber, K. Groh & J. Hemmen, Aug. 17 1985. Recent: CKG/9, Ilhéu de Cima, top, under stones, 33°03'13"N/16°16'48"W, approx. 100 m, leg. K. & C. Groh, Oct. 25 1980; CKG/7, CMN/29, ANSP H 11918/42, ZMH 120611/1 [ex coll. W Fauer], Ilhéu de Cima, top, under stones, 33°3'13"N/16°16'48"W, approx. 100 m, leg. K. & C. Groh & J. & C. Hemmen, Jun. 26 1983; ANSP H 11918/17, Ilhéu de Cima, top, under stones, 33°3'13"N/16°16'48"W, approx. 100 m, leg. J. Gerber, K. Groh & J. Hemmen, Aug. 17 1985; ZMH 24296/1, Porto Santo, without exact locality data, ex coll. Altonaer Museum, ex coll. O. Semper, ex coll. Dohrn; ZMH 24297/1, Porto Santo, without exact locality data, ex coll. Museum Klagenfurt; ZMH 24298/1, Porto Santo, without exact locality data, ex coll. Altonaer Museum.

[turricula]: From Lowe 1831: H. testa turrita, pyramidata, sub-cylindrica, bicarinata, perforata, tota minute et confertissime granulata, fusca, fere unicolore, vel supra obsolete fasciata: spira valde elevata, obtusissima; sutura distincta; anfractibus bicarinatis, carinis æqualibus, prominentibus, distinctis, sulco divisis: apertura rotunda; peristomate continuo, circinato, disjuncto, tenui, reflexo. Axis 4 lin. Diam. 3. Anfr. 8–8½; [pererosa]: From Wollaston 1878: ... a keel, very largely developed in the ‘α. pererosa,’ in the centre of each, causing the basal volution to be strongly bicarinated ….. var. ß. pererosa. – Plerumque obscurior, spira breviore, anfractibus in medio multo grossius carinatis (carina altissima), ultimo sensim latiore necnon antice obsolete subtortuoso, fere quasi superimposito, apertura submajore.

The shell is dextral and hairless. It is remarkably elongated and scalariform with deep sutures. The protoconch is from whitish to completely dark brown with 1.5 to 2 whorls. It is finely granulated along the first whorl and shows also fine radial striae and extremely small, scattered tubercles along its remaining portion. The teleoconch has from 6.9 to 7.2 rapidly increasing whorls. It is usually reddish brown, with brick red and/or dark violet shades in colour. The dark areas of the shell are mottled with more or less light brown to whitish areas, usually placed longitudinally and slightly slanting. In some specimens, the lighter areas tend to be more evident along the keels. No band pattern is visible along the upper whorls. On the lower part of the last whorl there is sometimes one dark, indistinct band that is usually very narrow. The area around the umbilicus is usually the lightest in colour. The shell is usually covered by fine debris serving as a camouflage.

The spire is very high and remarkably conical in shape. Two evident keels start already from the second whorl of the teleoconch. The keels gradually strengthen, reaching their maximum extent along the body whorl. The lower and the upper keel are more or less equally developed, the lower only sometimes slightly more pronounced. The lower whorls (especially the fourth and fifth) form a “shoulder” giving the whorls an angular contour. The sutures are deep and well marked.

The external surface does usually not show fine growth lines, except for some strong, more or less regularly spaced ribs along the top and bottom of the body whorl. Irregularly arranged, fine tubercles are present all over the teleoconch, also along the edges of the keels the tubercles remain well-separated not forming a peripheral chord.

The last whorl is not distinctly wider than the penultimate whorl, nevertheless abruptly descending near the aperture. The umbilicus is very narrow, almost closed, and somewhat eccentric. The aperture is elliptical with a faint thickening along the columellar portion of the stoma. Sometimes this thickening can also extend as far as the parietal side of the aperture. The peristome is continuous and detached from the body whorl, reflected, with the columellar margin somewhat thicker and more distinctly reflected (Figs 101–102).

Figures 99–102. 

99 Wollastonia turricula original figure as in R. T. Lowe, 1831 (from Lowe 1831: pl. 6 fig. 21). Shell of Wollastonia turricula 100 shell of the lectotype from loc. typ., ex coll. R. T. Lowe NMH 1948.7.8.35 101, 102 shells from Ilhéu de Cima. Scale bar 1 mm.

D 6.6 ± 0.4 mm (range 6.1–7.0 mm); H 8.8 ± 0.2 mm (range 6.1–9.0 mm); FW 4.3 ± 0.1 mm; PA angle 32.1 ± 2.1°; NT > 100; NW 7.0 ± 0.1 (n = 8). Ratio D/H 0.8; ratio FW/H 0.5.

The head and the neck are usually dark grey to grey. The sides and the posterior upper section of the foot are whitish. The foot is white and the sole is longitudinally divided into three areas. The central area is smooth, whereas the two lateral areas are equipped with bands of muscles that are roughly arranged in a chevron pattern. The mantle border is dark grey with five more or less developed lobes. The walls of the pallial cavity are colourless, without any stripes or spots. A strong pulmonary vein is visible. The jaw is odonthognatous and its shape is markedly arched. There are up to 25 smooth transverse ridges. The right ommatophoral retractor is independent from both penis and vagina.

The albumen gland is short and as long as the sperm-oviduct. The prostatic part of the sperm-oviduct extends into a vas deferens that is approximately as long as the sperm-oviduct, which is inserting into the penial complex. The free oviduct is two times longer than the vagina. The duct of the bursa copulatrix is rather wide, slightly shorter than the penis, and uniform in diameter. It terminates in a roundish bursa copulatrix. The transition area between the duct and the bursa is very sharply delimited, abruptly widening and turning into the bursa. The spermatophore is unknown. One tuft of digitiform glands arises from the proximal part of the vagina. There are usually two rather wide glands that are approximately equally long and very rarely branched. A short and thin vaginal appendix arises from the wall of the vagina, just distal of the glandular tuft.

Very smooth, rather widely and irregularly spaced and little elevated pleats run longitudinally along the inner surface of the vagina, reaching into the genital atrium as far as the genital orifice. The atrium is rather wide. Its internal walls are equipped with large and soft pleats, running longitudinally towards the genital orifice. The penial flagellum is short, remarkably cylindrical and with a blunt apex. It is usually as long as the epiphallus. Its internal walls are equipped with a digitiform papilla that originates at the proximal end of the flagellum and which is orientated towards the penial papilla. The epiphallus is approximately half as long as the penis. Its internal walls are usually equipped with two to three longitudinal pleats. These pleats are arranged more or less “metameric”.

The retractor muscle is large, strong and is of variable length. The penis lacks any muscular or glandular sheath. It is thick-walled and approximately four times longer than the flagellum. It is cylindrical and slightly swollen in its proximal portion. The inner walls of the penis are equipped with a large longitudinal, fleshy, and smooth pleat, running from the penial papilla almost as far as the atrium. Some minor, smooth, longitudinal pleats are usually also present. The penial papilla is short but somewhat bulky. Its surface is smooth, with the opening emerging apically; its channel is rather narrow. The inner lumen of the penial papilla is filled with a spongy and sturdy tissue, which directly connects with the walls of the epiphallus. The longitudinal section of the penial papilla shows that its walls are the continuation of the penial walls that abruptly bend inward. See Figs 103–111.

Figures 103–111. 

Anatomy and genitalia of Wollastonia turricula, Ilheu de Cima. 103 whole genitalia excluding gonads 104 mantle border 105 section of vagina 106 whole genitalia excluding part of OSD, AG and gonads 107 ornamentation of the inner walls of the flagellum 108 ornamentation of the inner walls of the flagellum, the penial complex, the vagina and the genital atrium 109 longitudinal section of penial papilla 110 section of penial papilla 111 tip of penial papilla. Scale bars 1 mm.

Wollastonia turricula is found under volcanic rocks scattered on grassland in open fields.

Restricted to the slopes and plateau of the islet Ilhéu de Cima, off the southeastern coast of Porto Santo. The species occupies an area of less than two square kilometres (Fig. 112). The form pererosa of W. turricula is known to occur on the steep slopes at lower elevations of the islet Ilhéu de Cima.

Figures 112–116. 

112–114 shells of Helix turricula var. pererosaRAM EXEMS-1720-1909-d39-74 115 Ilheu de Cima 116a, 116b labels from RAM. Scale bar 1 mm.

Wollastonia turricula is easily distinguishable from all the species belonging to either Hystricella or Wollastonia gen. n. by its peculiarly turreted shell and genital features. The anatomical and genital features of the species, under the name Ochtephila turricula, have previously been thoroughly described by Watson (1923), nevertheless Watson’s study limited its observations mostly to the external features of the genital system. Unfortunately, except for some drawings presented by Mandahl-Barth (1950), no additional information on the genital anatomy was published until now. Watson’s (1923) description, despite being thorough and accurate, sometimes gives a wrong impression of what the author observed. On p. 289 the author describes “three small finger-shaped processes” pointing out that “the shortest of the three is usually less than half the length of the others”. He considered all these three processes “homologous with the so called mucous glands found in so many of the Helicidae”. Watson considered also the vaginal appendix as a gland that is probably an apomorphic state of the stylommatophores. He also wrongly considered the “conspicuous hemispherical swelling” on the outer side of the vagina to be “doubtless a degenerate dart-sac”. It is known that the dart sac can assume such a “swollen” appearance, as for example in the genus Cernuella, but its inner structure shows a totally different arrangement compared to that found in W. turricula (see Giusti et al. 1995: 445). Watson also described the internal ornamentation of the penis as “smooth”, not detecting the main fleshy pleat and its surrounding secondary small pleats. Nevertheless, Watsons’ (1923) description as a whole is thorough and accurate, including also interesting notes about the histology of the tissues. This kind of anatomical description was very rare at the time, where conchological features were still considered as the most important taxonomical characters in land snail systematics.

After its description, the taxon Helix turricula var. pererosa Wollaston, 1878 was mostly ignored by subsequent authors, except by Mandahl-Barth (1950) who treated it as a subspecies of W. turricula. Three syntypes of Helix turricula var. pererosa Wollaston (see Figs 112–114) could be traced at the Exeter Museum (coll n°EXEMS-1720-1909-d39-74). The preservation of the specimens clearly indicates that they were collected alive and not as subfossils. Following a careful morphological evaluation and a comparison with recent and subfossil specimens (Fig. 115), no substantial morphological differences could be detected with regard to the shell morphology, both concerning its micro- and macroscopic features (microsculpture, overall shape, keels, dimensions). Therefore, we treat it here as just a form of Wollastonia turricula and propose the name Helix turricula var. pererosa Wollaston, 1878 as a junior synonym of Wollastonia turricula. Pettitt (1977) reports on significant changes in the shell shape of W. turricula after the construction of the lighthouse on the islet Ilhéu de Cima after 1900. However, that observation may be based on material collected prior to the construction works and therefore may have contained more specimens of the form pererosa because the top of the islet was only easily accessible after the construction of the stairs to the lighthouse and therefore collecting probably was carried out nearer to the coast where the pererosa form predominates.

According to Seddon (2011e) the species is Vulnerable (VU). In our opinion, however, it should be regarded as Critically Endangered (CR B1a, b(ii, v), 2a, b(ii, v)) because the extent of occurrence and the area of occupancy of the species is less than 1 km² and although Watson (1923) reported the species to “occur in considerable numbers” on Ilheu de Cima, observations made during the 1980s (KG) showed that the species is considerably less frequent than in the past, probably as the result of a decline of habitat quality as a consequence of grazing by goats or other unknown reasons (see also Seddon (2008: 80)). Moreover, living specimens were only reported from the area around the top plateau of Ilheu de Cima, i.e., at a single location (Fig. 117).

Figure 117. 

Distribution of Wollastonia turricula. Filled circles refer to recent and open circles to fossil records.

1855 Helix (Hystricella) vermetiformis R. T. Lowe: 186.

1867 Helix (Octephila) vermetiformis – Paiva: 47–48.

1867 Helix (Octephila) vermetiformis var. α minor Paiva: 48.

1878 Helix (Hystricella) vermetiformis – Wollaston: 163.

1894 Geomitra vermetiformis – Pilsbry in Pilsbry 1893–1895: 242.

1931 Geomitra (Actinella) bicarinata var. vermetiformis – Nobre: 87.

1950 Discula (Hystricella) vermetiformis – Mandahl-Barth: 31, 55.

1983 Discula (Hystricella) oxytropis vermetiformis – Waldén: 267.

2002 Geomitra vermetiformis – Bank et al.: 124.

2006 Discula oxytropis – Cameron et al.: 40 [partim].

2008 Hystricella oxytropis – Seddon: pl. 29 fig. C, map 177 [partim; in her “Corrigenda” Seddon (2009) mentions for pl. 29 fig. C in Seddon (2008) that the ”Shell of Hystricella oxytropis is normally approx. 8 mm wide, not 5 mm, and does not always have a double keel”].

2009 Hystricella oxytropis – Seddon: 80 [partim].

2009 Hystricella vermetiformis vermetiformis – Groh et al.: 21, fig. 29.

2017 Hystricella vermetiformis – Groh: e.T107396913A107396917.

NHM 1968.588, lectotype (herewith designated), from loc. typ. ex coll. R. T. Lowe. The lectotype is depicted in the Fig. 118.

Figures 118–120. 

Shells of Wollastonia vermetiformis. 118 lectotype of Helix vermetiformis R. T. Lowe, 1855, NMH 1968.588 ex coll. Lowe 119 recent specimen from Pico do Baixo 120 subfossil specimen from Porto dos Frades. Scale bar 1 mm.