The genus Litophyton Forskål, 1775 (Octocorallia, Alcyonacea, Nephtheidae) in the Red Sea and the western Indian Ocean

Abstract The Litophyton species of the Red Sea and the western Indian Ocean are revised, which includes species previously belonging to the genus Nephthea, which is synonymized with Litophyton. A neotype for both Litophyton arboreum, the type species of Litophyton, and Nephthea chabrolii, the type species of Nephthea, are designated. The new species Litophyton curvum sp. n. is described and depicted, and a key to all Litophyton species is provided. Of the 26 species previously described from the western Indian Ocean and Red Sea, 13 species are considered valid and 13 have been synonymized or placed in other genera.


Introduction
This is the second in a series of publications in which nephtheid genera are revised. The first (Ofwegen 2005) dealt with the genus Chromonephthea, erected for Nephthea species with coloured sclerites. In their paper dealing with a molecular approach of nephtheid taxonomy, Ofwegen and Groenenberg (2007) already stated that in a morphologically based revision of Nephthea the genus should be synonymized with Litophyton. This is the first part of such a morphologically based revision, dealing only with species from the the western Indian Ocean and Red Sea, in which both genera are synonymized based on the molecular and morphological data mentioned by Ofwegen and Groenenberg (2007). The material of the type species of both Litophyton, L. arboreum Forskål, 1775, andNephthea, N. chabrolii Andouin, 1828, is lost. Both of these spe-cies were originally described from the Red Sea and the examination of extensive Red Sea material allowed the selection of neotypes for them. As the original descriptions of these two species revealed hardly any characters, the neotype selections were based on specimens that could not be allocated to any other species known from the Red Sea and Indian Ocean in accordance with identifications of other authors.
Nephthya savignyi Ehrenberg, 1834 is at present the type species of the genus Dendronephthya, as designated by Utinomi (1954a). After examination of many specimens from the Red Sea referable to this species it proved to belong to Litophyton, making Dendronephthya a junior synonym of Litophyton. This finding was supported by the molecular study of McFadden et al. (2011) in which specimens identified in that publication as Dendronephthya savignyii grouped with Nephthea and Litophyton. A case will be submitted to the International Commission on Zoological Nomenclature (ICZN) to preserve the name Dendronephthya. Meanwhile the species will be cited as Litophyton ?savignyi. Examination of the types of most species of Litophyton and Nephthea and examination of many recently collected specimens proved that species of this genus have restricted distributions and that therefore the revision can be split based on different geographic regions. The 17 nominal species of Litophyton (van Ofwegen 2015a) and 49 nominal species originally referred to Nephthea (van Ofwegen 2015b) at present recorded as occurring in the Indo-West Pacific will be dealt with in separate publications.

NTM
Museum and Art Gallery of the Northern Territory, Darwin, Australia.

Material and methods
For the technical terms used in the descriptions, see the glossary compiled by Bayer et al. (1983). Four permanent microscope slides have been made for each specimen examined, which are kept at RMNH: (1) one slide of the sclerites from a number of polyps and part of branch, (2) one of the sclerites from the surface and interior of the top of the stalk, (3) one of the sclerites from the surface and interior of the base of the stalk, and (4) a slide of polyps made transparent to study the arrangement of the sclerites.
Sclerite drawings have been made using the permanent microscope slides. As most old museum specimens examined contained a large amount of broken sclerites, SEM images were produced of recently collected material.
All the Nephthea and Litophyton type specimens available have been re-examined. In addition, more recent material from the RMNH and ZMTAU collections has been included.  Van Beneden, 1867: 197. Amicella Gray, 1869: 123. Verrilliana Gray, 1869: 130. Litophytum Kükenthal, 1903 Diagnosis. Nephtheids with bushy and arborescent colonies. Polyps clustered at the end of the terminal branches, forming catkins. Polyps non-retractile, without or with supporting bundle, sometimes completely unarmed. Sclerites of surface layer of branches, stem and stalk are spindles and unilateral spinose spindles, the colony stalk also contains capstans and derivatives of capstans. Interior of the stalk has sparsely tuberculated spindles. Colonies zooxantellate.

Systematic part
Type species. Litophyton arboreum Forskål, 1775, by monotypy. Remarks. Because of the synonymy of Nephthea with Litophyton, for many species a spelling emendation needed to be made to comply with ICZN Art. 31.2 in relation to gender agreement between generic and species names.
Characters used. Litophyton species are known to have extreme intraspecific variation in colony shape and sclerites (Verseveldt 1973). For the Red Sea and Indian Ocean the number of nominal species is 26, but in the present study this number has been reduced to 13 valid species, including a new one, whereas 13 species have been synonymized or assigned to other genera (see below).
Colony shape did not prove to provide a reliably constant character. A good example is L. ?savignyi, which may resemble some other Litophyton species but can also have a colony shape like that seen in some species of Stereonephthya (Figures 50-51).
The polyp armature showed some useful characters but some sclerite arrangements were observed in various species: L. chabrolii ( Figure 2B), L. laevis (Figure 2A), L. simulatum ( Figure 2D), and L. striatum ( Figure 2C), Only one species, L. ?savignyi had a projecting supporting bundle; three had small rodlets in the polyp stalk, L. arboreum, L. curvum and L. filamentosum; two had rodlets in the polyp head, L. maldivensis and L. viridis; one lacked sclerites in the adaxial polyp part, L. bumastum and the remaining five species had spindles all over the polyp, L. chabrolii, L. laevis, L. lanternarium, L. simulatum, and L. striatum.
The sclerites of Litophyton species show a staggering morphological variation, with those in the polyp and stem and stalk surfaces varying most in shape. Notably, the shape of the stalk surface sclerites is different depending on the height on the stalk. The least variable sclerites are the spindles of the internal canals. As with the polyp armature some species have the same types of spindles, which limits the usefulness of these sclerites. Verseveldt, 1968 = L. savignyi 02. Spongodes albida Holm, 1894 = L. savignyi 03. Nephthya armata Thomson & Henderson, 1906= Stereonephthya BM 1912.2.25.12 (holotype) and BM 1933.148 (holotype fragment) were re-examined. Despite disintegrated sclerites, it was obvious that the species belongs to Stereonephthya 04. Nephthea galbuloides Verseveldt, 1973= L. striatum 05. Nephthea tixierae Verseveldt, 1968= L. savignyi 06. Litophyton acutifolium Kükenthal, 1913  Diagnosis. Litophyton with branched spindles in the surface layer of the base of the stalk and large internal spindles in the base of the stalk, up to 2.0 mm long, the largest not branched.
Remarks. The species is sufficiently described by Verseveldt (1974b: 28). Here I give drawings of a polyp ( Figure 3A), polyp sclerites ( Figure 3B), base stalk internal ( Figures 3C, 4B) and base stalk surface sclerites ( Figure 4A)  The species is characterized by the presence of branched spindles of the surface layer of the base of the stalk and the presence of large internal spindles in the base of the stalk, sometimes with blunt ends or branched. L. arboreum also has internal spindles with blunt ends, but here the surface spindles of the base of the stalk are never branched. L. simulatum can also have spindles with blunt ends but these are always less than 0.5 mm long, while in L. acuticonicum they are up to 1.5 mm long. Sometimes also spindles with side branches are present in the interior of the base of the stalk (ZM-TAU 26239, Figure 11c), similar to those of L. striatum but that species never shows internal spindles of 2.0 mm long. It is noteworthy that these longer spindles with blunt end were not photographed with the SEM but were present in the microscope slides. Diagnosis. Litophyton with many internal spindles of the base of the stalk with blunt ends. The polyp stalk with scales.

Litophyton arboreum
Description. The neotype is 5 cm high and 7.5 cm wide; the colony stalk is 2-3 cm high ( Figure 12).
The polyps ( Figure 13) are up to about 0.5 mm wide and high. Supporting bundle not projecting, composed of clavate spindles with simple, tall tubercles, outer side and one end thorny ( Figure 14A). Length of these spindles is up to 0.7 mm. Polyp body sclerites irregularly arranged, the smallest are present adaxially, they are sparsely tuberculated spindles ( Figure 14B); abaxially they merge into the smaller spindles of the supporting bundle and likewise have a thorny outer side ( Figure 14C). The tentacles have rodlets up to 0.05 mm long ( Figure 14D). The polyp stalk has scales up to 0.05 mm long ( Figure 14E).
Surface layer top of stalk. Spindles, radiates, and derivatives of these, merging into unilaterally spinose spindles; all sclerites with simple tubercles (Figures 14F, 15A). The spindles are up to 0.3 mm long.
Surface layer base of stalk. Sclerites similar to those of the top of the stalk but with longer and sharper spines ( Figure 15B-C).
Interior base of stalk. Spindles, up to 1.2 mm long, with simple sparse tubercles ( Figure 16A-B). A few spindles have one or more side branches, many have one or two blunt ends. The smaller spindles are more often branched than the larger ones.
Colour. The colony is white. Distribution. Red Sea, Socotra. Remarks. The microscope slide of the stalk of ZMTAU Co 26234 only has internal sclerites of the stalk because the specimen has the surface layer missing.
Two of the 14 microscope slides of RMNH Coel. 2218, from Indonesia, are missing, notably those of the interior stalk sclerites. The unilaterally spinose sclerites of the surface layer of the stalk have much higher spines than those of the neotype of L. arboreum, and the slide with polyp sclerites also shows different sclerites, no polyp stalk scales at all. I regard this a misidentification.
RMNH Coel. 17122, from Australia, is clearly a misidentification, it has pointed interior sclerites in the base of the stalk.
L. arboreum is characterized by having large spindles with blunt ends in the interior of the stalk. L. acuticonicum and L. simulatum also have this type of sclerites. L. acuticonicum differs in having branched, unilaterally spinose spindles in the surface layer of the stalk, which are also twice as long as the unbranched spinose spindles of L. arboreum. L. simulatum also differs in having twice as long unilaterally spinose spindles in the surface layer of the stalk. Moreover, L. arboreum has small oval scales in the polyp stalk, a type of sclerite not present in L. acuticonicum and L. simulatum.
Diagnosis. Litophyton with adaxial side of polyps without sclerites; interior stalk with pointed spindles up to 1.5 mm long; a few have blunt ends.
Distribution. Madagascar. Remarks. The species is sufficiently described by Verseveldt (1973: 98). Here I show the drawing of the polyp as presented by Verseveldt (1973: fig. 22a). The colony, which was not shown by Verseveldt (Figure 17), together with SEM images of the sclerites (Figures 18-19).
L. bumastum is the only Litophyton species in the western Indian Ocean described with the adaxial side of the polyps lacking sclerites. Figures  Diagnosis. Litophyton with polyps with spindles. Internal spindles of the base of the stalk up to about 1.0 mm long, mostly unbranched and with very regular tuberculation.
The polyps are up to about 0.5 mm wide and high ( Figure 21). Supporting bundle not projecting, composed of spindles with simple or complex tubercles ( Figure 22D). Length of these spindles is up to 1.2 mm. Polyp body sclerites irregularly arranged, the smallest are present adaxially ( Figure 22B); abaxially they merge into the smaller spindles of the supporting bundle ( Figure 22C). The tentacle sclerites resemble the smallest adaxial polyp sclerites ( Figure 22A).
Surface layer top of stalk. Spindles, radiates, and derivatives of these, spindles, and unilaterally spinose spindles; sclerites with simple or complex tubercles ( Figure  23). The spindles are up to 0.6 mm long.
Surface layer base of stalk. Sclerites similar to those of the top of the stalk but the unilaterally spinose sclerites with slightly longer spines ( Figure 24).
Interior base of stalk. Spindles, up to 1.2 mm long, with simple, regular, sparse tubercles ( Figure 25). Several spindles have one or more side branches, a few have one or two blunt ends. The smaller spindles are more often branched than the larger ones.
Colour. The colony is white.

Distribution. Gulf of Aqaba.
Remarks. The species resembles L. lanternarium and L. simulatum but differs in having mostly unbranched internal stalk spindles with very regular tuberculation.
It is noteworthy that Lam and Morton (2008) probably misidentified a specimen of Chromonephthea as they mentioned coloured specimens with coloured sclerites, characters of that genus and not of Lithophyton.
RMNH 2212, 2216 is the material from Indonesia described by Verseveldt (1966) as Nephthea chabrolii. It has similar polyp armature as the neotype here described. However, the internal stalk sclerites are branched, not present in any Red Sea specimens identifiable as L. chabrolii. Likewise a number of RMNH specimens identified as N. chabrolii from the Indo-Pacific and a few ZMB specimens from Indonesia (see removed from the species) all proved to be other species and therefore I have to conclude N. chabrolii as here described has only been found in the Red Sea so far. Diagnosis. Litophyton with the internal spindles of the base of the stalk mostly with pointed ends. Polyp stalk with scales. Surface layer of the stalk with straight and curved sclerites.
Description. The flabby holotype ZMTAU Co 28555 is 5.5 cm long and wide ( Figure 26A); the colony is bent to one side.
The polyps are up to about 0.5 mm wide and 0.6 mm high ( Figure 27). Supporting bundle not projecting, composed of spindles with simple tubercles, outer side and distal end with larger tubercles ( Figure 28A). Length of these spindles is up to 1.0 mm. Polyp body sclerites irregularly arranged, the smallest are present adaxially ( Figure  28B); abaxially they merge into the smaller spindles of the supporting bundle and have a thorny outer side ( Figure 28C). The tentacle sclerites are small rodlets up to 0.1 mm long ( Figure 28D). The polyp stalk has scales up to 0.05 mm long ( Figure 28E).
Surface layer top of stalk. Radiates, derivatives of these, spindles and unilaterally spinose spindles ( Figure 29A-B); the latter up to 0.6 mm long.
Surface layer base of stalk. Radiates, derivatives of these, spindles and unilateral spinose spindles ( Figures 29C, 30A); the spindles and unilateral spinose spindles are up to 0.5 mm long; many are slightly curved.
Interior base of stalk. Spindles, up to 1.0 mm long, with widely spaced simple tubercles ( Figure 30B-D); some spindles branched.
Etymology. The Latin "curvum", curve, curved object or line, refers to the curved spindles from the surface of the stalk.
Distribution. Red Sea: Gulf of Aqaba, Dahlak Archipelago. Remarks. ZMTAU Co 26223, ZMTAU Co 26225 and ZMTAU Co 28552 are slightly different from the holotype. They show less compressed colony shapes ( Figure 26D).
To show variation, the sclerites of ZMTAU Co 28552 are also presented ( Figures  31-32).
The species can be confused with L. chabrolii (Andouin, 1828), but that species has stiffer colonies, stronger polyp armature, and wider, more regular shaped internal stalk spindles. L. laevis  is also similar to this species, but lacks the curved spindles and unilateral spinose spindles in the surface layer of the base of the stalk. Moreover, both these species do not have the polyp stalk scales present in L. curvum.
Distribution. Only known from the type locality Madagascar. Remarks. The species is sufficiently described by Verseveldt (1973: 141). Here I present the holotype colony shape ( Figure 33) and SEM images of its sclerites ( Figures  34-35).
The species mostly resembles Litophyton curvum but differs in having straight sclerites in the surface layer of the base of the stalk and very spiny, almost spheroidal, sclerites in the surface layer of the base of the stalk. RMNH Coel. 12966 and RMNH Coel. 14596 are misidentifications. The specimens have no rodlets on the adaxial side of the polyp, as is the case in L. filamentosum.
The species can be confused with L. simulatum, but the latter has wider, more branched internal spindles.
RMNH Coel. 8941 has spindles up to 1.3 mm long in the interior of the stalk, quite some of them with blunt ends and therefore I re-identified it as L. arboreum.
Distribution. Only known from the type locality Madagascar.
Remarks. The species is sufficiently described by Verseveldt (1973: 147). Here I give an image of the holotype ( Figure 42) and present SEM images of its sclerites (Figures 43-44). Verseveldt mentioned and depicted (1973: fig. 29a) rodlets in the polyp stalk. I only noticed a few and with the SEM work they also did not stand out as they do in the species with many polyp stalk rodlets; only one is depicted by me ( Figure 43E).
The species mostly resembles L. chabrolii but differs in having internal spindles in the base of the stalk with irregular tuberculation; several spindles branched.
The specimens from Madagascar identified by Verseveldt as Nephthea amentacea (1973: 91) are very much like Litophyton lanternarium. They only differ in having longer spindles in the interior of the base of the stalk and these spindles having denser tuberculation. I could not find the type material of Nephthea amentacea and therefore the characters of that species remain unknown, but I consider it highly unlikely this species, which was described from the Sulu Islands, occurs in Madagascar anyway. Figures 1E, 45-49 Eunephthya maldivensis Hickson, 1905: 824, fig. 12  Diagnosis. Litophyton with polyps with small rodlets. Internal spindles of the base of the stalk short, mostly unbranched, several with blunt ends.
The polyps have small rodlets and spindles, situated in the tentacles and both the lateral and abaxial parts of the polyp ( Figure 46A-B). Length of the spindles up to 0.25 mm.
Lobes. Surface and interior with narrow spindles up to 0.5 mm long ( Figure 46D). Surface layer top of stalk. Radiates, derivatives of these, and spindles ( Figure  46E); up to 0.30 mm long.
Surface layer base of stalk. Radiates, derivatives of these, spindles and unilateral spinose spindles ( Figure 47A); the spindles and unilateral spinose spindles up to 0.25 mm long.
Interior base of stalk. Spindles with widely spaced simple tubercles ( Figure 47B-D); some spindles branched; some smaller ones almost smooth; many with blunt ends. The interior spindles are up to 0.85 mm long.
Remarks. The characteristics of specimen BMNH 1962.7.20.124 agree with the description of Hickson (1905) of his single specimen. Therefore it is puzzling why nowadays the BMNH has two syntypes of Litophyton maldivensis. The other syntype, BMNH 1962.7.20.123, was also examined and shows characters of the genus Scleronephthya. Therefore, BMNH 1962.7.20.124 is here considered to be the holotype of L. maldivensis.
The species can be confused with L. arboreum Forskål, 1775, as that species has also many blunt spindles in the interior of the base of the stalk. But they are longer, have more regularly spaced tubercles and do not include smaller, smoother forms. Also the polyps are more strongly armed. Litophyton maldivensis can also be confused with specimens of L. simulatum in terms of having short sclerites in the interior of the stalk. But L. simulatum, like L. arboreum, differs in lacking the smooth smaller internal spindles and having more strongly armed polyps. Moreover, it has many branched internal spindles.
SEM images of the sclerites of ZMTAU Co26249 ( Figure 45B) are also presented (Figures 48-49). The polyp body sclerites of ZMTAU Co26249 ( Figure 48B) are different from the rodlets of the holotype (Figure 46C), and the sclerites from the top of stalk surface ( Figure 48D) are different to those shown for the holotype in Figure 46E. I consider these difference intraspecific variation. Diagnosis. Litophyton where the polyps have a projecting supporting bundle and make an acute angle with the polyp stalk.
Description of NHMW 2407. The colony is 3 cm high and wide, the colony stalk 2 cm high ( Figure 50B).
Polyps up to about 0.6 mm wide and high ( Figure 52A). Supporting bundle projecting up to 0.7 mm, composed of 2-4 spindles ( Figure 52A). These spindles are up to 3 mm long, with spines and projecting smooth tip ( Figure 52D). Sclerites in polyp are irregularly distributed. Abaxial side of the polyp with curved spindles with spines or simple tubercles, up to 0.6 mm long, several with one smooth end ( Figure 52B). Laterally less tuberculated spindles are present, up to 0.2 mm long ( Figure 52B). Adaxially and in the tentacles flattened rodlets and ovals are present, up to 0.1 mm long ( Figure  52C). The adaxial side of the polyp stalk has small rodlets, up to 0.05 mm long ( Figure  52E). The amount of these rodlets varies per polyp, sometimes only a few are present ( Figure 52A), others have the whole polyp stalk closely packed with them.
Surface layer top of stalk. Spindles with simple tubercles, up to 2.5 mm long, some slightly unilaterally spinose.
Surface layer base of stalk. Spindles and unilaterally spinose spindles with simple tubercles, shorter than in the top of the stalk, up to 1.5 mm long. Furthermore small rodlets, several unilateral spinose; smaller branched spindles, radiates and derivatives of these ( Figure 53A).
Interior base of stalk. The larger interior spindles are not very different from the surface ones, only slightly less tuberculate ( Figure 52F). They are up to 1.5 mm long. Smaller, branched bodies also occur ( Figure 53B).
Colour. Colony is white. Distribution. Red Sea, Indian Ocean. Variability. Most colonies examined have slender branches and resemble species of Stereonephthya ( Figure 51A-B); a few are more "Litophyton-like" ( Figure 51C).
Remarks. After the very short original description of Nephthya savignyi by Ehrenberg (1834: 60), Klunzinger (1877: 35) identified a specimen from Koseir (Red Sea), as Spongodes (= Dendronephthya) savignyi. Kükenthal (1905: 529) examined many specimens, 20 all together, including two specimens from the Berlin museum, one of them Ehrenberg's, "originalexemplar", and one from the Stuttgart museum, Klunzinger's, specimen. Kükenthal mentioned little variability in all specimens examined and he also synonymized Holm's, Nephthya jaegerskioeldi and N. jaegerskioeldi var. microspina with Ehrenberg's, Dendronephthya savignyi, based on the presence of polyps in bundles. One of the type specimens of N. jaegerskioeldi has been re-examined; the colony and sclerites are presented in Figures 50D, 54-55, and I agree with Kükenthal that the species should be synonymized with L. ?savignyi.
During my visit to the Berlin museum I was unable to find Ehrenberg's, specimen, later on Dr. Goetz Reinicke was so kind to provide me with photographs of a specimen that could be that particular one, though with a question mark ( Figure 50A). Indeed doubts remain about the status of the Berlin specimen since it is almost 12 cm wide, while Kükenthal mentioned its width to be 8.5 cm.
The specimen described above is from the Vienna Museum (NHMW 2407) ( Figures  50B-C, 52-53), and is probably one of the specimens examined by Kükenthal, as it was found at Tor (Red Sea) and Kükenthal (1905: 531) also examined material from that locality.
Although not re-examined I consider Spongodes albida Holm, 1894 synonymous with Litophyton ?savignyi. The specimen is only a few cm long but features all the characters of L. ?savignyi, i.e. projecting supporting bundle, many small rodlets in the polyp stalk and large interior spindles.
In the Red Sea L. ?savignyi differs from all other Litophyton species in having polyps with a protruding supporting bundle giving the colony a prickly appearance. The polyps also make an acute angle with the stalk as is seen in the genus Stereonephthya. It can only be confused with two species of Stereonephthya, S. acaulis Verseveldt, 1973, andS. cundabiluensis Verseveldt, 1965. The latter always contains coloured sclerites but S. acaulis can have white colonies with colourless sclerites (Verseveldt 1973: 153). But it differs from L. savignyi in lacking oval tentacle sclerites, having differently shaped polyp stalk rodlets (Stereonephthya-type; Figs 13a, 14a, 15a in Ofwegen and Groenenberg (2007)), and having much smaller (up to 0.75 mm long), branched, less tuberculate, internal stalk spindles; see Verseveldt (1973: figs 33n, o).
Unfortunately, Utinomi (1954a) designated L. savignyi as the type species for Dendronephthya, a genus with more than 250 nominal species. Following strict nomenclatural priority would cause widespread confusion within nephtheid taxonomy. To avoid changing of generic combinations and the confusion that it would cause, a case will be submitted to the International Commission on Zoological Nomenclature (ICZN) to preserve the name Dendronephthya, in the meanwhile the species will be cited as Litophyton ?savignyi.
The two Nephthea species with projecting supporting bundle described by Verseveldt (1968) from Madagascar, N. aberrans and N. tixierae, I regard synonymous with L. ?savignyi. I consider the reported differences to represent intra-specific variation.
The polyps are up to about 0.65 mm wide and 0.8 mm high. Supporting bundle not projecting, composed of spindles with simple tubercles, outer side and distal end with more tubercles. Length of these spindles is up to 1.1 mm. Polyp body sclerites irregularly arranged, the smallest are present adaxially; abaxially they merge into the smaller spindles of the supporting bundle and have larger tubercles on the outer side. The tentacle sclerites resemble the smallest adaxial polyp sclerites.
Surface layer top of stalk. Spindles, radiates, and derivatives of these, merging into unilaterally spinose spindles; all sclerites with simple tubercles. The spindles are up to 0.25 mm long.
Surface layer base of stalk. Sclerites similar to those of the top of the stalk but longer, up to 0.4 mm long; the unilaterally spinose sclerites having longer spines.
Interior base of stalk. Spindles, up to 1.0 mm long, with simple sparse tubercles. Several spindles have one or more side branches, the smaller spindles are more often branched than the larger ones. A few spindles have blunt ends.
Colour. The colony is grey. Distribution. Red Sea, Socotra, Chagos Archipelago. Remarks. The microscope slides of transparent polyps made by Verseveldt (1970) show smooth rodlets in the adaxial polyp body, his drawing of a polyp ( Figure 7I) also shows a few, and they are even mentioned in his description. However, they represent the end views of polyp sclerites as smooth rodlets are not present in the slides of polyp sclerites. Verseveldt (1970) compared the species with L. laevis  and concluded the tuberculation of the sclerites, being much stronger in L. simulatum, was the main character to distinguish between them. Also the interior sclerites differ, in L. laevis they are slender, and only up to 0.5 mm long, in L. simulatum they are twice as wide and up to 1.0 mm long.
The species also resembles L. striatum as that species has also branched interior spindles in the base of the stalk. However, the sclerites of the interior of the base of the stalk of L. striatum always include spindles with many small side branches or extra tall tubercles, while those of L. simulatum have just one or a few. RMNH Coel. 8921 and 8945, both identified by Verseveldt as Nephthea chabrolii, proved to be L. simulatum.
The polyps are up to 0.80 in height and up to 0.90 in width ( Figure 71A). Supporting bundle mostly not projecting, sometimes one spindle projecting for 0.10 mm; it is composed of up to about 10 spindles; these spindles are up to 1.15 mm long and up to 0.13 mm wide; with simple tubercles and spines ( Figure 71B). Distal end of projecting spindles with higher spines. Polyp body sclerites irregularly arranged. On the abaxial and lateral sides the spindles are up to 0.35 mm long; with thorns on the outer side ( Figure 71C). Adaxially only some small, spiny rodlets are present, about 0.1 mm long. On the adaxial side of the polyp stalk, just below the polyp body, similar rodlets are present, placed transversely; tentacles with nearly smooth rodlets, 0.03-0.08 mm long ( Figure 71D).
Surface layer top of stalk. Radiates and derivatives of these, spindles and unilaterally spinose spindles, which are up to 0.6 mm long. Several sclerites with some sidebranches ( Figure 71E).
Surface layer base of stalk. Sclerites similar to those of the top of the stalk but with longer spines ( Figure 72A). Few unilaterally spinose spindles present.
Interior base of stalk. Spindles with widely placed simple spines and tubercles; the spindles often have side-branches ( Figure 72B-C). Length of these spindles up to 1.6 mm.
Colour. Colony cream. Distribution. Red Sea, Socotra, Chagos Archipelago, Madagascar. Remarks. In the catalogue of the ZMB the numbers 6833-6838 are mentioned as material of N. striata, 6834 and 6838 as types. I could only find two specimens (numbers 6837 and 6838). In the SMF one specimen is present (SMF 1279), that clearly is the same specimen as the one described and depicted by Kükenthal (1903: 166, pl. 7 fig. 12). Kükenthal, in his description of the species, mentioned two other specimens (both about 3 cm high and wide) from the Red Sea. According to Kükenthal (1903) these two specimens were deposited in the Breslau Museum. Nowadays no type material of this species is present in Breslau. Most probably ZMB 6838 ( Figure 59A) is one of the two Breslau specimens. The sclerites of ZMB 6838 (Figures 60-61) show it to be a specimen belonging to L. simulatum. ZMB 6837 lacks the base of the colony and therefore some doubts about its identity remains but probably it represents the same species SMF 1279, which is here designated as the lectotype of L. striatum.
The lectotype SMF 1279 has some supporting bundle spindles with a somewhat leafy projecting end (not depicted); ZMTAU 26194 and ZMTAU 26195 have some with a smooth spine (not depicted).
ZMTAU Co 25851 ( Figures 70B, 73-76), ZMTAU Co 26216 and ZMTAU Co 26203 (Figures 70C,(77)(78)(79) have been used to produce SEM images of the sclerites. Noteworthy is the difference in internal base stalk spindles (Figures 76, 78). ZMTAU Co 26203 shows an unusual amount of unilaterally spinose sclerites in the surface of the base of the stalk, with densely placed spines which are not like those in SMF 1279 ( Figure 79).
The type material of Nephthea galbuloides has been re-examined (Figures 80-82) and proved to be L. striatum. This specimen also shows very densely arranged spines on the unilaterally developed forms.

Litophyton viridis
The difference between Litophyton viridis, L. acutifolium, L. crosslandi, L. sanderi, and L. stuhlmanni is only based on the polyps, those of L. viridis having no sclerites at all, while the other four species have few sclerites in the polyps. I regard the polyps without sclerites of L. viridis an extreme case of a species with a few sclerites in the polyps and synonymize L. acutifolium, L. crosslandi, L. sanderi, and L. stuhlmanni with L. viridis. May (1898) mentioned two specimens of L. stuhlmanni, the specimen examined, ZMH C2391 (Figures 84, 89) is different from the one depicted by May (1899: pl. 3 fig. 25). May (1899) and Kükenthal (1903), who re-examined May's, material, described the polyps as being devoid of sclerites. I assume that both missed the polyp sclerites hidden in detritus inside the polyps.
Apart from being much smaller ( Figure 83C), Litophyton sanderi has much in common with L. stuhlmanni. Kükenthal (1903) already recognized this close resemblance but kept the species separate because he could not find any sclerites in the polyps of L. stuhlmanni. For comparison the sclerites of the holotype of L. sanderi are depicted (Figures 90-91). The small sclerite differences with L. stuhlmanni I consider to be intraspecific variation.
The colony fragment of Litophyton crosslandi present in the Natural History Museum (BM 1933.3.13.193) is only part of the colony originally described. The total length of the fragment is 5.3 cm ( Figure 83D; notes of Verseveldt) while Thomson and McQueen mentioned branches up to 13 cm long. The two microscope slides examined only show sclerites found in the top of their colony (Figure 92). Some polyps of the holotype of Litophytum crosslandi also show the "ring of slerites in the tentacle basis" mentioned by  for his L. acutifolium.
ZMTAU Co 32941 and 33091 are only fragments of the top of colonies, the flabby nature of the fragments together with the sclerites matching those of L. viridis made me identify them as this species.
ZMTAU Co 34114 (previously identified as L. acutifolium by me) has been used by McFadden et al. (2011) for their molecular study.
L. maldivensis and L. acuticonicum both also have polyps with limited amount of sclerites. L. acuticonicum differs from L. viridis in having much larger interior stalk sclerites (up to 2 mm long). L. maldivensis has overall much smaller interior stalk sclerites which mostly have blunt ends. L. striatum has similar looking sclerites in the interior of the base of the stalk as ZMTAU 26193 but in that species the polyps are much stronger armed.     (Verseveldt, 1974), holotype RMNH Coel. 8920. A sclerites surface layer base of stalk B spindles of interior base of stalk. (Verseveldt, 1974). A ZMTAU Co 25867 B ZMTAU Co 26239 C-E ZMTAU Co 25867 C tentacle rodlets D polyp body spindles E spindles of supporting bundle. Scale at E also applies to D. (Verseveldt, 1974), ZMTAU Co 25867. A-B sclerites of interior base of stalk C tubercles on spindle.   (Verseveldt, 1974), ZMTAU Co 26239. A-B sclerites of surface layer top of stalk C-D sclerites of surface layer base of stalk. Scale at A also applies to D. Figure 11. Litophyton acuticonicum (Verseveldt, 1974), ZMTAU Co 26239. A sclerites of surface layer base of stalk B-C sclerites of interior base of stalk D tubercles on spindle. Scale at B also applies to A.       (Verseveldt, 1973), holotype RMNH Coel. 8045. (Verseveldt, 1973), holotype RMNH Coel. 8045. A-B tentacle rodlets C-D polyp body sclerites E spindles of supporting bundle F-G sclerites of surface layer top of stalk. Scale at B also applies to C. (Verseveldt, 1973), holotype RMNH Coel. 8045. A sclerites of surface layer base of stalk B-C sclerites of interior base of stalk D tubercles on spindle. Scale at B also applies to A.                . A holotype ZMB 6818 B ZMTAU Co 26126.  , holotype ZMB 6818. A lateral, adaxial and abaxial views of polyp armature B supporting bundle spindle C polyp body sclerites D tentacle rodlets E sclerites, surface layer top of stalk. Scale at A only applies to A. , holotype ZMB 6818. A sclerites of surface layer base stalk B spindles of interior base of stalk.     (Verseveldt, 1973), holotype RMNH Coel. 8052. (Verseveldt, 1973), holotype RMNH Coel. 8052. A tentacle rodlets B-C polyp body sclerites D spindles of supporting bundle E polyp stalk rodlet F sclerites surface layer top of stalk. Scale at D also applies to C and F. (Verseveldt, 1973), holotype RMNH Coel. 8052. A-B sclerites of surface layer base of stalk C-D spindles interior base of stalk E tubercles on spindle. Scale at B also applies to C. (Hickson, 1905). A holotype BMNH 1962.7.20.124 B ZMTAU Co 26249. (Hickson, 1905). A, C-E holotype BMNH 1962.7.20.124 B ZM-TAU Co 26249 A-B polyp armature C polyp rodlets D spindles of lobe E sclerites surface layer top of stalk. Scale at A applies to A-B. (Hickson, 1905) holotype BMNH 1962. A sclerites surface (bracket after Hickson, 1905) layer base of stalk B-C spindles interior base of stalk D tubercles on spindle.        (Ehrenberg, 1834), UUZM 417, type of Nephthya jaegerskioeldi. A lateral views of polyp armature B polyp body spindles C supporting bundle spindle (partly) D tentacle rodlets E rodlets from polyp stalk. Scale at B also applies to C, scale at D also to E. Figure 55. Litophyton ?savignyi (Ehrenberg, 1834), UUZM 417, type of Nephthya jaegerskioeldi. A sclerites surface layer base of stalk B-C spindles interior base of stalk. Scale at C only applies to C. Figure 56. Litophyton ?savignyi (Ehrenberg, 1834), ZMTAU 26245. A tentacle rodlets B-C polyp body spindles D rodlets from polyp stalk E-G sclerites surface layer top of stalk. Scale at B also applies to F, scale at E also to C, scale at A also to D.      (Verseveldt, 1970), ZMB 6838, syntype of Litophyton striatum (Kükenthal, 1903). A sclerites surface layer base of stalk B spindles interior base of stalk, outlines only C tubercles on spindle. Scale at A also applies to C. (Verseveldt, 1970), ZMTAU Co 25874. A tentacle rodlets B-C polyp body spindles D spindles of supporting bundle. Scale at D also applies to C.    (Verseveldt, 1970), ZMTAU Co 26201. A-B tentacle rodlets C polyp body spindles D spindles of supporting bundle. Scale at C also applies to D. (Kükenthal, 1903). A syntype SMF 1279 B ZMTAU Co 25851 C ZM-TAU Co 26216. (Kükenthal, 1903), syntype SMF 1279. A lateral view of polyp armature B supporting bundle sclerite (partly) C polyp body sclerites D tentacular rodlets E sclerites surface layer top of stalk. Scale at A only applies to A. (Kükenthal, 1903), syntype SMF 1279. A sclerites surface layer base of stalk B-C spindles interior base of stalk C outlines only. Scale at C only applies to C. (Kükenthal, 1903), ZMTAU Co 25851. A tentacle rodlets B polyp body spindles C spindles of supporting bundle. Scale at B also applies to C.     (Kükenthal, 1903), ZMTAU Co 26203. A-B tentacle rodlets C polyp body spindles D spindles of supporting bundle E-F sclerites surface layer base of stalk G spindles interior base of stalk. Scale at D also applies to C, F; scale at A also to E. (Kükenthal, 1903), RMNH Coel. 8048, holotype Nephthea galbuloides. A tentacle rodlets and one small polyp body spindle B polyp body spindles C spindles of supporting bundle D-E sclerites of surface layer top of stalk F interior base stalk spindle. Scale at C also applies to B.            Thomson & McQueen, 1908, holotype BM 1933. A lateral views of polyp armature B polyp body sclerites C branch sclerites. Scale at C also applies to most left sclerite of B. Figure 93. Litophytum acutifolium Kükenthal, 1913, ZMB 6683, part of holotype. A lateral views of polyp armature B polyp body sclerites C supporting bundle spindles D sclerites surface layer top of stalk. Scale at C also applies to D.