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Show 252 LIEUT.-COL. H. H. GODWIN-AUSTEN ON [Feb. 1, Hainan, China, according to Benson1, but which possesses all the characteristics of the Socotran shells, and must be, I consider, wrongly labelled; there is also one recorded from the continental shore of Mogadoxa, viz. O. guillani; and we have an outlier in one species on the other side of the Arabian Sea in peninsular India, O. hinduorum, recorded from Kattiawar and named by Mr. W . T. Blanford. Again, in Cyclotopsis, a genus belonging to the Cyclostomidae, but with a multispiral operculum, we find the connexion of Socotra not with Africa but with peninsular India on the one side, where it is represented by C. semistriatus, and in the far south-east, in the Seychelles, by another species : this has been already pointed out by Mr. W . T. Blanford in a paper (Ann. & Mag. Nat. Hist. 1864) " O n the Classification of the Cyclostomacese of Eastern Asia," and more recently (in the same publication, 1876) " O n the African Element in the Fauna of India." Lithidion, again, follows a very similar distribution, with the exception of India, all the species being East-African island forms, though not extending southward beyond Madagascar. On the north it is found in Arabia, but has not, I believe, been recorded from the African coast, which, however, has been little explored. Tropidophora is a purely Madagascar genus, where it has reached its maximum of development and beauty in some magnificent shells ; and it occurs in most of the East-African islands, viz. Mauritius and Rodriguez,-in the first represented by the very rare T. barclayana, and in the second by T. articulata. Tropidophora we now find spreading as far north as Socotra; but this genus has never been found in India. Judging from the land-molluscan fauna of Socotra, there is strong evidence that the island was once directly connected with Madagascar to the south. W e know the great antiquity of that island ; and it is not unreasonable to suppose that in Socotra, the Seychelles, Madagascar and Rodriguez we have the remnants of a very ancient more advanced coast-line on this western side of the Indian Ocean, which line of elevation was probably continuous through Arabia towards the north. With an equally advanced coast on the Indian side, the Arabian Sea would, under these conditions, have formed either a great delta, or narrow arm of the sea into which the line of the Indus and Euphrates drained. Such conditions would have admitted of the extension of species from one side to the other, which the later and more extensive depression of the area, as shown in Scinde, afterwards more completely shut off. OTOPOMA NATICOIDES. (Plate XXVII. figs. 1, 1 a.) Cyclostoma naticoides, Recluz, Rev. Zool. 1843, p. 3. Shell globosely turbinate, very solid; sculpture well marked transverse irregular lines of growth crossed by distant indistinct spiral sulcation. Colour white, fine orange within the aperture. Spire rather high, the extreme apex generally decollate. Whorls 1 Sowerby in his original description gives no locality. |