OCR Text |
Show 1881.] SHELLS FROM SOCOTRA. 257 [" Very common everywhere on the ground." (I. B. B.)] This species is nearest to L. sidcatum, 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 umbilicated. 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. desciscens, Pfr. (from Mus. 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 A whorls; the margin well reflected outwards, its edge forming a continuous raised smooth spiral rib. Size :- Major diam. 8*2, minor diam. 6'8, alt. axis, 3#8 millim. •33, „ „ 0-27, „ „ -14 inch. [" From under granite boulders, hills above Adona, over 2000 ft., and on stem of Draca?na 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 OF THE PLATES. PLATE XXVII. Fig. 1,1a. Otopoma naticoides, Recluz, nat. size, p. 252. 1 b. , operculum of ditto. 2, 2 a. , balfouri, n. sp., p. 253. 3, 3 a. , complanatum, n. sp., p. 254. 4, 4 a. , clathratulum, Recluz, var. socotrana, p. 254. PLATE XXVIII. Fig. 1, 1 a. Otopoma conicum, n. sp., p. 255. 1 b. Operculum of same. |