252 LIEUT.-COL. H. H. GODWIN-AUSTEN ON [Feb. 1, 



Hainan, China, according to Benson^ 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 semis triatus, 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) 

 " On the Classification of the Cyclostomacese of Eastern Asia," and 

 more recently (in the same publication, 18/6) "On the African 

 Element in the Fauna of India." 



Lithidion, again, follows a very similar distribution, with the ex- 

 ception 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. We know the great antiquity of that island ; and it is 

 not unreasonable to suppose that in Socotra, the Seychelles, Mada- 

 gascar 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 bigh, the extreme apex generally decollate. Whorls 



' Sowerby in his original description gives no locality. 



