1881.] SHELLS FROM SOCOTRA. 257 



['* Very common everywhere on the ground." (I. B. B.)] 

 This species is nearest to L. sulcatum. Gray, or more correctly Cy- 

 clostoma (Lithidion) lithidion, Sowerby, Mr. Gray having adopted 

 the specific name for his new genus ; but this last shell is not so 

 openly umbilioated. It is also very similar in form and coloration to 

 L. niveum, Pfr., from Madagascar, but differs much in the aperture 

 and sculpture, L. niveum being very smooth. L. depressum, Pfr. 

 (the habitat of which is unknown), is also close ; but the spire is quite 

 flat. L. souleyetianum. Petit, from the island of Abd-el-Goury 

 near Socotra, does not appear to be found in Socotra ; it is much 

 higher in the spire and altogether different in form. L. desciseens, 

 Pfr. (from Miis. Cuming), is given as from Socotra, but is not in this 

 collection. An examination of the species of Lithidion represented 

 in the British Museum shows that the peculiarly irregularly wound 

 apex is a generic character common to all. 



Cyclotopsis ornatus, n. sp. (Plate XXVIII. fig. 5.) 



Shell openly umbilicated, depressedly conoid, thin ; sculpture, 

 spiral sulcation, every other rib being more strongly developed, crossed 

 transversely by fine costulation ; colour pale sienna with a pale ochre 

 band on the periphery and with zigzag markings of the same colour 

 on the second whorl, this coloration only seen well on young shells; 

 spire somewhat low, apex smooth ; whorls 4, well rounded, the 

 last very slightly descending ; aperture circular, oblique ; peristome 

 thin, scarcely reflected on the inner margin. 



Operculum shelly, concentric, of 4 whorls; the margin well re- 

 flected outwards, its edge forming a continuous raised smooth spiral 

 rib. 



Size : — 



Major diam. 8*2, minor diam. Q'S, alt. axis, 3'8 millim. 

 „ „ -33, „ „ 0*27, „ „ -14 inch. 



[" From under granite boulders, hills above Adona, over 2000 ft., 

 and on stem of Draecena cinnabari, Balf. fil., on limestones at same 

 elevation." (I. B. B.)] 



This is a most interesting form, connecting the fauna of these 

 islands with India. It has a representative also in one species at 

 the Seychelles. 



EXPLANATION OP THE PLATES. 

 Plate XXVII. 



Fig. ], la. Otopoma naticoidcs, E^cluz, nat. size, p. 252. 

 1 b. , operculum of ditto. 



2, 2 a. , balfoicri, n. sp., p. 253. 



3, 3 a. , complanatum, n. sp., p. 254. 



4, 4 a. , clathratulum, Recliiz, var. socotrana, p. 254. 



Plate XXVIIL 



Fig. 1, la. Otopoma conicum, n. sp., p. 255. 

 1 b. Operculum of same. 



