(all from TANZANIA: Zanzibar: Pemba Island). Holotype (NMW.Z.2009.013.00001): adult shell stored dry; in leaf litter, near Wete (Locality 10 in Fig. 1 and Table 1), 13 February 2009, leg. B. Rowson, B. H. Warren & C. F. Ngereza. Paratypes (NMW.Z.2009.013.00002-00032): 31 adults and juveniles in 80% ethanol; other data as holotype. Paratypes (NMW.Z.2009.013.00033-00077): 45 adults and juveniles stored dry; other data as holotype. Paratypes (NMW.Z.2009.013.00078-00079), 2 adults gold-coated for SEM; other data as holotype. Paratypes (NMT): 2 adults stored dry; collection data as holotype. Paratypes (BMNH.20100582): 1adult & 1 juvenile stored dry; collection data as holotype. Paratypes (MNHN): 1 adult & 1 juvenile stored dry; collection data as holotype. Paratypes (NMSA.L8207/T2591): 2 adults stored dry; collection data as holotype. Paratypes (RMNH): 2 adults stored dry; collection data as holotype. Paratypes (NMW.Z.2009.013.00080-00096): 17 adults and juveniles in 80% ethanol; in leaf litter, Msitu Mkuu FR (Locality 8 in Fig. 1 and Table 1), 10 February 2009, leg. B. Rowson, B. H. Warren, C. F. Ngereza & paid local collectors. Paratypes (NMW.Z.2009.013.00097-00174): 78 adults and juveniles stored dry; other data as previous. Paratype (NMW.Z.2009.013.00175): 1 adult gold-coated for SEM; other data as previous. Paratypes (NMW.Z.2009.013.00175-00176): 2 adults in 80% ethanol; in leaf litter, near Matuleni (Locality 12 in Fig. 1 and Table 1), 15 February 2009, leg. B. Rowson & C. F. Ngereza. Paratypes (NMW.Z.2009.013.00177-00210): 33 adults and juveniles stored dry; other data as previous. Paratype (NMW.Z.2009.013.00211): 1 adult stored dry; in leaf litter, near Wambaa (Locality 13 in Fig. 1 and Table 1), 13 February 2009, leg. B. Rowson, B. H. Warren, C. F. Ngereza & paid local collectors.

Shell relatively large (to 4.20mm wide) and strongly depressed. When fresh, with spirally-ridged operculum and characteristic periostracum of radial lamellae peripherally extended into long hairs gathered into points, or much shorter hairs gathered into fringes. When denuded, with relatively few spiral keels.

Description of holotype: Adult shell (Figs 16–18) relatively large for the genus in Africa, 2.25mm x 3.95mm including periostracum, strongly depressed, of approximately 4.5 regularly expanding whorls, with wide, perspective umbilicus. Peristome effectively complete, slightly thickened and flaring, especially basally. Aperture and operculum effectively circular. Operculum calcareous, outer surface with multispiral, blade-like raised lamella of approximately 9 revolutions, weakly convex as a result; inner surface smooth. Protoconch smooth, with irregular malleation discernible only at extreme magnification (Fig. 25). Teleoconch periostracum of fine, extremely close (<0.025 mm apart) radial lamellae, running from suture to suture. Lamellae each prolonged into long, flat periostracal extensions (“hairs”) extending well beyond the whorl periphery, forming spiral keels (up to four on the body whorl), with less-pronounced periostracal keels continuing into umbilicus. Periostracal hairs (in life and in fresh shells, whether wet or dried) regularly gathered at their tips to form bunches of six or more hairs (Fig. 25).

The periostracum of C. pembense forms a continuum of variation. At one extreme are individuals with hairs gathered together at their tips (as in the holotype). At the other are those in which the periostracal lamellae form instead a rough, raised periostracal fringe where the lamellae appear cemented together (Figs 19–21; 27). These extremes are more frequent than intermediate forms, but such intermediates do occur, in which the bunches of hairs are irregularly missing, probably worn away (see below). The two extreme forms are sympatric at three of the species’ four localities – i.e., at the type locality, at Msitu Mkuu FR, and near Matuleni (Localities 10, 8 & 12 respectively in Fig. 1 and Table 1). At the fourth locality near Wambaa (Locality 13 in Fig. 1 and Table 1), only one individual was found, and was of the fringed form. Both forms include both live- and dead-collected individuals, and both adult and juvenile shells. The size ranges overlap, although the fringed form seems to reach a slightly larger maximum (4.00–4.20mm wide with 4.25–4.5 whorls). Other features of the shell (shape, operculum, and protoconch; Fig. 26) are consistent across all individuals. Shells from which the periostracum has been lost were common but always empty, and cannot be assigned to either form. Such denuded shells (Figs 22–24) have relatively few (up to 8) weak spiral keels on the body whorl (including umbilical part), with fine, extremely close incised radial lines between the keels. All nine live-collected individuals of the fringed form were dissected and a penis was detected in six of them. A penis was not detected in any of nine individuals of the hairy form.

This species is attributed to Cyclophoridae: Cyathopomasensu lato following Emberton (2003). All forms of Cyathopoma pembense differ from the few other East African Cyclophoridae in being larger and more depressed than Cyathopoma azaniense Verdcourt, 1978 (Figs 13–15), an undescribed azaniense-like species from the East Usambaras (Verdcourt 2006; NMW material examined), and the Malawian Cyathopoma tres van Bruggen, 2008 (van Bruggen 2008). They are also larger than the Central African Cyathopoma papillaris (von Martens, 1892) and have fewer spiral keels (see van Bruggen 1986). The elaborate periostracum appears to be unique among East African taxa but similar features occur in some southeast African and western Indian Ocean island taxa. Cyathopoma pembense differs from species of the southeast African Chondrocyclus Ancey, 1898 either in the operculum or in periostracal features; Cyathopoma putealis Connolly, 1939 and Cyathopoma trifimbriatus Connolly, 1939 have fringes like Cyathopoma pembense but very different opercula (see van Bruggen 1986; Herbert and Kilburn 2004). Cyathopoma pembense is more depressed and differs in periostracum from the Seychelles Cyathopoma blanfordi H. Adams, 1868 (see Gerlach 2006a, b). Photographs of Cyathopoma pembense were compared with the BMNH types of several Comoros species attributed to “Cyclotopsis” (Cyathopoma nevilli Morelet, 1877, Cyathopoma ilicum Morelet, 1877, and Cyathopoma horrida Morelet, 1887). Although worn, none of these were an exact match for Cyathopoma pembense. Nor does it agree with the descriptions or figures of any other cyclophorid of the Comoros (see Fischer-Piette and Vukadinovic 1974), Madagascar (Emberton 2003, 2004), the Mascarenes (Griffiths and Florens 2006), the Seychelles (Gerlach 2006a, b), nor any Asian species known to us.

The variation shown by this species is striking. One might consider the extreme periostracal forms separate species, albeit indistinguishable when the shells are denuded. However the presence of intermediates suggests that this is not the case. The variation could result from sexual dimorphism (hairy forms female, fringed forms male) which would explain their occurrence in sympatry. However, sexual dimorphism would not explain the existence of intermediate forms. It would also demand that the three fringed individuals without a penis were immature males rather than females, when equally possible is that fringed forms consist of three females and six males while and all nine hairy individuals were immature. Natural wear and corrosion on the periostracum, presumably from hairy to fringed forms, would explain the latter possibility and account for the continuum of variation. It would not, however, easily explain the existence of live animals of both types (in each case both adults and juveniles in sympatry, where presumably the whole population is exposed to similar factors causing wear and corrosion. Possibly both sexual dimorphism and wear on the shells play a part in this unusual pattern. More speculatively, other alternatives include incomplete speciation or hybridisation between two closely related species.

Apparently endemic to Pemba island.

pembense, from Pemba island, a noun in the generative case.

(all from TANZANIA: Zanzibar: Pemba Island). Holotype (NMW.Z.2009.013.00211): slug 30.0 mm long in 80% ethanol, on understorey foliage during day, Ngezi FR (Locality 2 in Fig. 1 and Table 1), 8 February 2009, leg. B. Rowson, B. H. Warren, C. F. Ngereza & local collectors.

Paratype 1 (NMW.Z.2009.013.00212): slug 37.5 mm long in 80% ethanol; other data as holotype. Paratype 2 (NMW.Z.2009.013.00213): slug 31.0 mm long in 80% ethanol; other data as holotype. Paratype 3 (NMW.Z.2009.013.00214): slug 25.0 mm long in 80% ethanol; other data as holotype. Paratype 4 (IRSNB.IG.31599/MT2317): slug 18.0 mm long in 80% ethanol; other data as holotype. Paratype 5 (NMT): slug 19.0 mm long in 80% ethanol, on understorey foliage during day, Ngezi FR (Locality 6 in Fig. 1 and Table 1), 8 February 2009, leg. B. Rowson, B. H. Warren, C. F. Ngereza & local collectors. Paratype 6 (NMW.Z.2009.013.00215): slug 18.5 mm long in 80% ethanol; leaf litter during day, Ras Kiuyu FR (Locality 7 in Fig. 1 and Table 1), leg. B. Rowson, B. H. Warren, C. F. Ngereza & local collectors.

Medium-sized slug (to at least 55mm in life) with strong keel prolonged into long caudal appendage, with mantle completely covering shell. Pale to colourless, with dorsum covered in pustules. Viscera not extending far into tail, shell mineralised, jaw with no or weak projection. Radula unique in having up to 280 tiny, tricuspid teeth per half-row. Genitalia broadly similar to other Dendrolimax.

Note: points of agreement with an unnamed East Usambara species as discussed by Verdcourt and Polhill (1961) (see below) are marked with “*”.

External features: Medium-sized slug (extended length to at least 55mm in life, or 37.5mm in 80% ethanol)*. Tail strongly keeled* and hollowed out behind mantle*; keel prolonged into long straight caudal appendage* above small caudal pore*. Viscera extending little more than half-way into tail*. Body bell-shaped in cross-section when extended, but able to flatten body considerably. Sole not narrow, evenly tripartite*. Peripodial grooves clear, from tail to genital orifice and head. Mantle fully attached posteriorly, free anteriorly, not grooved, subangulate rather than rounded behind, completely covering shell, lacking a dorsal pore or slit*. Pneumostome in posterior third of mantle*. Genital orifice far forward, near right lower tentacle. No head wart or similar structure detected. Integumental tubercles barely detectable on mantle, tail or cephalopodium; instead, whole dorsum rather densely and regularly covered in hemispherical (rather than prickly) pustules*. Dorsum largely colourless and translucent*, with green, grey or pink tinge*, acquiring a green cast when on foliage; keel white; sole colourless. Diffuse, slate-grey pigment on caudal appendage, bordering keel* and/or in obscure blotches or bands on mantle in some specimens*, absent in others; remains on preservation. Pustules conspicuously white*, remaining so on preservation. Ommatophore retractors grey-ochre on preservation.

Jaw and radula: Jaw solid, semi-lunate, lacking median projection (holotype), or projection very weak (paratype). Radula of holotype broad (3.65 mm wide × 2.20 mm long), of 155 rows (over 50 angular rows per mm length). Teeth extremely small* and extremely numerous*, to nearly 450 in each half-row*, with a central tooth. All teeth (including central tooth) tricuspid*, with very little change across the row, perhaps becoming more s-shaped laterally. Ectocones larger (or at least projecting further) than mesocones in all teeth except central tooth. This is unlike any radula figured in van Goethem (1977) where mesocones are always the largest cusps, and the maximum number of teeth per half-row is around 280, and only in radulae over 5.00 mm wide. The radula form may suggest a microphagous, rather than phytophagous diet.

Shell and pallial complex: Shell unguiform, bilaterally symmetrical, to at least 4.10 mm long, infilled, mineralised and white* (i.e. not fragile as in other Dendrolimax). Pallial area well vascularised.

Genitalia: Right ommatophore retractor passes between penis and vagina. No atrial diverticulum or stimulator*. Long flagellum present in place of calc sac*. Epiphallus long, stiff, not spiralling around penis*. Penial retractor short, attaching well below flagellum, perhaps obtaining from diaphragm. Penis with basal sheath, contiguous with penis wall apically, internally with longitudinal pilasters and a basal papilla; similar to that of several Dendrolimax (see van Goethem 1977). Bursa copulatrix duct arising low on vagina, bound to it by sheath-like circular muscle fibres. Bursa copulatrix long, weakly clavate, reaching upper part of spermoviduct*. Vagina and free oviduct with a clear, thick-walled sheath*. Hermaphroditic duct extremely short*, barely perceptible between spermoviduct and large yellow ovotestis, which lies near rear of mantle. Albumen gland small, hook-shaped*. No spermatophores were recovered from the Pemba material which may not be fully adult.

This distinctive species was found only in FRs. At Ngezi, the slugs were found on the underside of large understorey leaves, up to 2m above ground. The body was held flattened with one optic tentacle protruding (Fig. 12). At Ras Kiuyu FR the species was found in litter. It appears to be undescribed although it (or a similar species) may occur in the East Usambara Mts. Beyond that its affinities are less certain.

Van Goethem (1977) thoroughly revised the known urocyclid slugs of Africa and Madagascar and provided keys to internal characters. The Pemba species keys readily out to Dendrolimacini (sole genus Dendrolimax Heynemann, 1868). The only East African record of the mainly Central-West African Dendrolimax is an unnamed and incompletely described species collected by Verdcourt (1960) from Thika Gorge, Kenya, who indicated a swollen lower oviduct not present in the Pemba species. Moreover the Pemba species differs from all other Dendrolimax in the radula, body form, and shell, although the genitalia are similar. It shows much clearer similarities to a taxon referred to as “Genus et species nov.” by Verdcourt and Polhill (1961, p. 32–33, fig. 42) from Sigi in the East Usambara Mts. (1961). They said, “This mollusc does not belong to the family Urocyclidae judging by [the] radula but to an isolated subfamily of the Helicarionidae near to the Durgellinae”. Van Goethem (1977) could not obtain material of this taxon for his revision but considered it a urocyclid. He treated it as “Species E”, incertae sedis after Dendrolimacini and Upembellini along with a “Species D” from Grand Comore to which he noted a similarity in the genitalia, but not the radula. Neither Verdcourt and Polhill (1961) nor van Goethem (1977) were certain whether the specimens of “Species E” or “Species D” were adult. This is an important consideration since slugs may change in appearance as they grow. However, neither Verdcourt and Polhill, van Goethem with his experience of growth series of many taxa, nor other slug workers (e.g. Forcart 1967) could attribute these forms to any known species or genus. Verdcourt and Polhill (1961) noted that there was no absolute criterion, e.g. concerning the size of the albumen gland, for recognising adulthood in urocyclid slugs. Since 1977 there has been little further work on the group in East Africa. The Pemba species, which will probably prove to include also the East Usambara species, is here described provisionally in Dendrolimax. Consideration was given to erecting a new genus but owing to a lack of unique features in the genitalia, and the large number of available genus-group names, is avoided until more data are available.

Although this species is fully limacised, there are also similarities in the body form and genitalia to numerous Afrotropical semi-slug genera, among them Verrucarion van Mol, 1970 of West and central Africa (van Mol 1970) and Malagarion Tillier, 1979 of Madagascar. The resemblance to the latter extends to the radula and white pustules (see Tillier 1979, Emberton 1994). Van Mol (1970) treated all African genera in Urocyclidae: Urocyclinae or Gymnarioninae. Tillier (1979) considered Malagarion to belong, with the Mascarene Colparion Laidlaw, 1938 in Helicarionidae: Ariophantinae and not Urocyclinae(/idae). He noted that the radula, but not genitalia, of Malagarion was similar to the Asian Durgellini (founded on the Burmese semi-slug Durgella Blanford, 1863). Verdcourt and Polhill (1961) had also noted a radula similarity between their East Usambara species and the Durgellinae, although this was not discussed by van Goethem (1977). Certainly the radula would be unique in Urocyclinae sensu van Goethem (1977), and resembles Malagarion in the size and number of teeth, and the large ectocones (at least on the more marginal teeth of Malagarion). The monophyly of these major groups is questionable while the systematics of tropical Limacoidea is still far from resolved (e.g. Tillier 1979, Hausdorf 1998, Schileyko 2002), but it remains possible that this species is related to one of them rather than other Dendrolimax.

Pemba island; probably also East Usambara Mts.

vangoethemi, a noun in the generative case, for Dr. J. L. van Goethem of IRSNB, in recognition of his thorough and highly accessible monograph on Afrotropical urocyclid slugs.

Living indiduals were abundant in leaf litter across Pemba, including sites many kilometres from the sea or fresh water (Table 2). As the only African terrestrial assimineid, Verdcourt (2000, 2006) considered Assimania aurifera worthy of a new genus in Omphalotropinae, a group diverse on the Mascarenes and elsewhere (Griffiths and Florens 2006). Assimania aurifera is otherwise recorded only from coastal Kenya and Unguja (Verdcourt 2006). However, its shells are very similar to Assiminia parvula Morelet, 1877, described from Anjouan, Comoros (Morelet 1877). Also terrestrial, Assimania parvula is widespread in the Indo-Pacific and was recorded from Aldabra by Gerlach and Griffiths (2002). Solem (1959) discussed how terrestrial assimineids could be dispersed naturally by sea although we note that Assimania aurifera is a common fossil in Pleistocene deposits in southern Tanzania (Reuter et al. 2010). Further data are needed to resolve this. Note: Both Assimania aurifera and Assimania parvula were described under misspellings of Assiminea Fleming, 1928: Assiminia (Morelet 1877) and Assimania (Preston 1912). The genus Eussoia, to which Assimania aurifera has been referred, now includes only aquatic taxa (Brown 1980).

Cyathopoma azaniense Verdcourt, 1978: 15–16; fig. 1

This species is otherwise known only from the vicinity of Shimoni, Kenya (Verdcourt 1978, 1982), the part of the mainland nearest to Pemba (c. 40km).

This group needs revision. Pemba shells are almost identical to those from Jozani Forest, Unguja, including in microsculpture and the range of colour patterns, differing mainly in a smaller maximum size and (Unguja 14.0 × 12.5 mm; Pemba 12.0 × 11.5 mm). There is slight variation in the strength of the spiral raised ridges, though none of the shells are as smooth as zanguebarica Petit, 1850 or letourneuxi Bourguignat, 1889 in historical collections (e.g. NMW, MNHN). It is hard to know whether this is infraspecific variation or not. Voeltzkow (1923) recorded “Lygatella letourneuxi (Bgl.)” (sic) from Pemba; Haas (1929) recorded it from Chake Chake. As well as zanguebarica and letourneuxi, Verdcourt (2006) lists two unnamed “species” from “Zanzibar”. Either could correspond to the Pemba taxon; possibly one biological species encompasses all four. One is said to have an affinity to letourneuxi and to Tropidophora scabra (H. Adams, 1867), an extinct Mauritian species that varies in sculpture according to Griffiths and Florens (2006). Intriguingly, these authors describe (p.53) a population of a smooth species of Tropidophora being replaced by a rough one over recent decades. Note: Verdcourt treats all East African Tropidophora in subgenus Otopoma Gray, 1850, but the Asian type species of this belongs in Cyclophoridae not Pomatiidae (=Pomatiasidae) (see Neubert 2003).

Voeltzkow (1923, p. 179) recorded this species from Pemba as “Vaginula brevis”Vaginula brevis Fischer, 1872 is considered a synonym of the widespread Laevicaulis alte (Forcart 1953, Verdcourt 2006). We tentatively refer two small juveniles from Ngezi FR to this species.

The name Gittenedouardia Bank & Menkhorst, 2008 recently replaced Edouardia auctt. non Gude (Bank and Menkhorst 2008). The slender-shelled East African species of Gittenedouardia differ subtly in shell proportions. Two of the Pemba shells are large enough to be adult, at 9.8 × 5.5mm (Fig. 29) and 8.2 × 4.1mm. These were compared with photographs of the lectotypes of Gittenedouardia conulina, Gittenedouardia metula (von Martens, 1895), and Gittenedouardia sordidula (von Martens, 1897) (all in ZMB) and Gittenedouardia tumida (Taylor, 1877) (in BMNH). Gittenedouardia conulina and Gittenedouardia metula appear to be the ends of a shape continuum from slender with less tumid whorls (conulina) to broad with tumid whorls (metula). The Pemba shells, Gittenedouardia sordidula, Gittenedouardia tumida, the other shells in the Gittenedouardia tumida type lot (see Rowson 2007, p.434), and probably Gittenedouardia metuloides (E. A. Smith, 1899) of Malawi and southern Africa, are each somewhere in the middle. A similar species is recorded from Aldabra (as Edouardia cf. tumida in Gerlach 2006b) and the Comoros Bulimus badiolus Morelet, 1881 also appears to belong to this group. This merits more detailed analysis but for now we associate the Pemba species with Gittenedouardia conulina. This happens to be both the only species previously recorded from Pemba and the oldest available name. It was noted on Pemba by Voeltzkow (1923) and Haas (1929) as Conulinus conulinus (von Martens)

Rowson (2007, p.433–434, 454–455) considered Gittenedouardia conulina one of the few taxa recorded from both Unguja and Pemba, but not the mainland. Given the taxonomic problem this is of little biogeographic significance. Regrettably the confusion in this group may have been added to by contradictorily illustrating Gittenedouardia conulina with a specimen from the mainland (Kilifi, Kenya) (Rowson 2007: Fig. 27). This bleached specimen’s identification (by the late T. Pain) as “Cerastus conulinus (Mts.)” was taken at face value, but it is too large (16.1mm) to be either Gittenedouardia conulina or Gittenedouardia sordidula. The name sordidula was introduced by von Martens (1897) to replace the homonym conulinus von Martens, 1878 (not von Martens, 1869) after having used the name conulinus for what he later considered two separate species in the same genus. As stated above, we consider the lectotypes of these two species, conulina and sordidula to be very similar, but the drawings in von Martens (1897) rather emphasise the differences which may have helped to mislead Pain. However, whichever species the Kilifi specimen represents, it is not one recorded from Unguja or Pemba.

All Pemba material appears to be conspecific. Across sites, shells reach only c14mm when adult, and are very thin, not glossy, with faint and irregular spiral and radial striae. One or more brown spiral bands per whorl are present on a weak yellow background, some individuals having a few additional weak brown spots. In several individuals the apex is dark. Multi-banded forms match what (Verdcourt (1961, 2006) calls Rhachidina braunsi var. quadricingulata (E. A. Smith, 1890), described from lowland Tanzania. All the Pemba material is here referred to braunsi, whose varieties we consider only colour forms. Voeltzkow’s (1923) record of “Rachis brauensis Mart.” (sic) probably refers to Rhachistia braunsi from Fundu I. (Haas, 1929). The genus is here given as Rhachistia rather than Rhachidina (see Solem 1959, Mordan 1992, Herbert and Kilburn 2004).

There is a hypothesis that Bulimus histrio L. Pfeiffer, 1854, described from the New Hebrides, is a synonym of Rhachistia braunsi. Solem (1964) cited Verdcourt (1961) as confirming a suggestion in Solem (1959) that braunsi and histrio were synonyms, thus proving that histrio was an early anthropogenic introduction from East Africa. Though not quite correct (the name braunsi did not appear in Solem 1959) this was followed by other workers in the region (e.g. Starmühlner 1970) and there is now a consensus that the Australasian populations originated in East Africa (e.g. Stanisic 1998, Herbert and Kilburn 2004). However, (Verdcourt (1961, 1983, 2006) remained ambiguous about placing the two in synonymy and objected that the colour pattern in Solem’s (1959) black and white picture of a type of Rhachistia histrio had not yet been noticed among East African species. He also noted the existence of other, earlier names. Our material is available should anyone be in a position to resolve this debate.

The Pemba material matches that from Unguja figured by Rowson (2007) under the name Afroguppya rumrutiensis, and the “Dupontia sp.” found on Aldabra (Gerlach and Griffiths 2002). Although these three populations appear conspecific, the species is not the mainly East African Afroguppya rumrutiensis. The West African Afroguppya solemi de Winter & van Bruggen, 1992 resembles it closely in size and shape, but has obscure spiral sculpture (de Winter and van Bruggen 1992) whereas these are finely granular. Igor Muratov (pers. comm.; Muratov in press) refers similar material from north-east Mozambique to Microcystina minima, a common species on the Mascarenes (see Griffiths and Florens 2006).

Although Voeltzkow (1923) did not mention this species Haas (1929) recorded it from Fundu I. as Trochonanina (Martensia) jenynsi (Pfeiffer) based on Voeltzkow’s material.

This species was found only in FRs (Table 2) in leaf litter and rotting wood. The only spermatophore obtained was partially digested but the slug recalls Pembatoxon insulare in all other respects including the radula. Van Goethem (1975) noted the holotype (BMNH) was collected in 1901 from “Pemba Island, E. Africa” by C. Crossland but gave no further locality.

Two additional urocyclid slugs were recorded from Pemba by Voeltzkow (1923, p.173) who noted their appearance after heavy rain. These were the only previously recorded speices not relocated in our survey. The difficulties in inventorying slug faunas are well-known (Cameron and Pokryszko 2005) so this does not necessarily imply their absence. They are Elisolimax roebucki (Simroth, 1910) (as Urocyclus roebucki) and Trichotoxon heynemanni Simroth, 1888 (as Trichotoxon voeltzkowi Simroth, 1910).

Found only in high forest at Ngezi (Table 2), supporting Verdcourt’s (2000) suggestion that it is a forest specialist.

The small size, tight coiling, and large umbilicus of this species are distinctive even within this difficult genus (Preston 1910). Verdcourt (2006) records Trichotoxon insulsa from the Shimba Hills (the type locality) and Mrima Hill, and NMW has specimens from Gazi (all localities in coastal Kenya). We found only in non-forest sites (Table 2).

Occurs in all habitat types (Table 2). Voeltzkow (1923) recorded it from Pemba as “Trochonanina mossambicensis Pts.” and “Trahonemia mossabicensis” (sic), noting numerous individuals. Haas (1929) recorded it as Trochonanina mossambicensis (Pfeiffer) from Chake Chake and Fundu I.

Widespread on Pemba (Table 2). Some individuals from high forest at Ngezi are small (to 61mm high) with a very irregularly thickened outer lip, suggesting adulthood.

Large shells agreeing with hamillei (see Rowson 2007) were the only Achatina found at Msitu Mkuu but apparently did not occur in other FRs (Table 2). Voeltzkow (1923) noted that “Achatina fulica (Fer.)” (sic) was widespread on Pemba; Haas (1929) gave a record from Fundu I.

Pemba specimens reach a large size (13.5 × 3.4 mm, occasionally 15.0 × 3.5 mm, up to 8 whorls), always being relatively narrower than Opeas lamoense. The maximum size is substantially greater than given by most authors (e.g. Gerlach 2006b: 9.4 mm; Griffiths and Florens 2006: 13.5 mm). Said to be restricted to “waste places” by Verdcourt (2000) this species nonetheless occurs in some forest habitats (Table 2). Allopeas gracile is widespread in the tropics but its native range is uncertain.Voeltzkow (1923) noted that “Opea gracile johanninum (Mor.)” (sic) was numerous in rotting logs on Pemba; Haas (1929) gives the record from Chake Chake. Fischer-Piette and Vukadinovic (1974) consider Bulimus johanninus Morelet, 1877, described from the Comoros, a synonym of Allopeas gracile. Recent authors (e.g. Neubert 1998, Gerlach 2006b, Griffiths and Florens 2006) rather than Verdcourt (2006) and Rowson (2007) are followed here in treating this species in Allopeas as distinct from Lamellaxis.

This species reaches 12.0 × 5.0 mm and is relatively broader than Pemba’s other subulinids. It was found only in high moist forest at Ngezi (Table 2). It keys out to Curvella subvirescens using Verdcourt’s (2002) key and resembles the types at BMNH. Verdcourt (2006) records Curvella subvirescens from the Nguru Mts. and Uluguru Mts. and notes its similarity to the Tanzanian Curvella sinulabris (von Martens, 1878) and Kenyan Curvella pertranslucens Preston, 1910, the latter described from the Shimba Hills (Preston 1910).

Pemba specimens reach 7.0 × 2.5 mm, being much smaller and narrower than Opeas lamoense. Griffiths and Florens (2006) figure specimens referred to Allopeas clavulinum (Poitiez & Michaud, 1838) and Allopeas mauritianum (L. Pfeiffer, 1847) that they suggest were introduced to the Mascarenes from East Africa. Both resemble some specimens of Opeas delicatum. Verdcourt was familiar with Allopeas clavulinum in botanic gardens in the UK, which in turn have been said to come from East Africa (Kerney and Cameron 1979) yet never included Allopeas clavulinum in his East African lists (Verdcourt 1983, 2000, 2006). This should be further investigated.

Pemba specimens reach 11.0 × 4.0 mm, being relatively much broader and with a relatively larger body whorl than Allopeas gracile. At one high forest site (Ngezi N2) some individuals have much stronger ribs, although the shell shape is similar.

Found only at Mtondoni (Table 2). The genital anatomy conforms exactly with that of Striosubulina striatella as figured by Schileyko (1999), though the bursa copulatrix is less voluminous. A tropical West African species, Striosubulina striatella has been widely introduced including to the Mascarenes (Griffiths and Florens 2006). This appears to be the first record from East Africa.

The geographical origin of this species is unknown. Gerlach (2006b) notes it has been found as a subfossil on Aldabra but Griffiths and Florens (2006) suggest it is originally Neotropical. Verdcourt (in litt. 2006) noted that he knew of no material of Subulina octona from East Africa so it is possible the species is spreading. The date of authorship follows Bank and Menkhorst (2008).

Verdcourt (2000) treated this as a forest species but it also occurs in other habitats on Pemba (Table 2). It is known from the Shimba Hills (Preston 1910; type locality) and from the Sigi Valley in the East Usambara Mts. (Verdcourt 2006).

This species was previously recorded from Pemba by (Verdcourt (1983, 2006).

This species is widespread and abundant on Pemba (Table 2). The specimens are assigned to the widespread Gonaxis denticulatus pro tem. rather than the more restricted Gonaxis gibbonsi Taylor, 1877. A revision of the East African taxa attributed to “Gonaxis” is currently under way (Rowson in prep.).

This species has not previously been recorded beyond the type locality (Shimba Hills) (Verdcourt 2006). According to Verdcourt (1958), its shell differs from that of the other known lowland species, Tayloria helicoides (C. R. Böttger, 1913) only in relative spire height and strength of sculpture. The latter is known only from Kipatimu, Kilwa District, south of the Rufiji Delta.

Pemba material matches Usambara material (NMW) of this Eastern Arc species very well. No species of Aenigmigulella has previously been reported from the coastal region (Verdcourt 2000, 2006) and it is unknown from Unguja. If native to Pemba it would thus suggest a special Eastern Arc affinity. However we note it was not found in forest reserves apart from a juvenile at Msitu Mkuu FR (Table 2). On Pemba, juvenile shells have complex dentition at a variety of stages. The living animal is cream-coloured. Recent systematic work (Rowson 2010) indicates “Gulella” aenigmatica does not belong in the genus Gulella L. Pfeiffer and a genus-level revision is in progress.

As noted by Verdcourt (1985) there is either substantial shell variation in the species Ennea radius Preston, 1910, or it comprises a complex of related taxa. This cannot be resolved without a thorough revision. Preston’s (1910) type from the Shimba Hills is said to be 3.25mm high and is strongly acuminate. Verdcourt (1985) figured a specimen from Diani Beach, Kenya which is much less acuminate but measures 4.23mm (calculated from his drawing). At up to 5.45mm, Pemba specimens are larger still, but resemble the type in being strongly acuminate and with less tumid whorls than the Diani Beach material. Specimens referred to Gulella radius from Unguja (Rowson 2007) are small (to 3.0mm) and not strongly acuminate. The peristomal teeth are in the same basic pattern in each of these populations, but vary in their size and complexity, none being quite as different as some of the other nominal species (discussed in Rowson and Lange 2007). What does appear relatively constant is the size, shape, and sculpture of Pemba specimens, which occur throughout the island (Table 2). They may form an island taxon worthy of subspecies or species status, which is given consideration in the discussions on endemism in the present paper. Recent systematic work (Rowson 2010) indicates “Gulella” radius does not belong in the genus Gulella L. Pfeiffer and a genus-level revision is in progress.

Six of the seven adults from Misali Island have an additional palatal tooth, recalling var. scissidens Connolly, 1922, described from Dar-es-Salaam. The additional tooth is not present on either of the two adults from Ras Kiuyu. This is a very widespread species and several such forms have been named. Neubert (1998) points out a discrepancy between Paladilhe’s (1872) description and figure of Ennea isseli Paladilhe, 1872 from Yemen, and figures an additional specimen which strongly resembles Gulella gwendolinae. This raises the possibility that Ennea isseli is a senior synonym of Gulella gwendolinae and, if so, also the question of whether it is truly native to Arabia. A direct comparison of types is advised.

This species, widespread in East and South-east Africa (van Bruggen and van Goethem 1997) was much more frequent in non-forest habitat types than in forest (Table 2). Voeltzkow (1923) recorded “Gulilla laevigata (Dohn)” (sic); Haas (1929) recorded Gulella laevigata (Dohrn) from Chake Chake. The record probably actually refers to Gulella planidens (see van Bruggen and van Goethem 1997).