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Show 4 LIEUT.-COL. GODWIN-AUSTEN ON SOCOTRAN SHELLS. [Jan. 16, above and below, side subvertical; aperture rhomboidal, rather wider than high ; peristome thin, continues as a thin callus on the body-whorl, arched above, straight below. Size:- Major diam. 3*4, alt. axis 0*5 millim. „ 0*13, „ „ 0*02 inch. There are unfortunately only two specimens of this curious form in the collection ; and these I found when carefully looking over some large tangled pieces of water-plants, which Prof. B. Balfour sent me to examine for this purpose, and which were in the same state as when transferred from the water. There is a very remarkable resemblance between tbe general form of this shell and the fossil species Macrocyclis carnatica of Stoliczka, which was described and figured from the Upper Cretaceous rocks of the Arrialur group in Southern India (Palaeontologia Indica, plate i. figs. 8, 8 a, 8 b, p. 12). The latter is represented as a dextral shell with flat-sided whorls angulate above and below. And if the two shells are compared in this position, it will he seen that the right margin of the periphery differs ; the diameter is greater above than below, whereas in socotrensis it is the reverse. Stoliczka says that the fossil specimen is much injured by pressure ; and a comparison of figs. 8 a and 8 b, where the periphery is restored, shows it to be more like the Socotran shell. I am inclined to think that this fossil form may be a freshwater shell allied to Planorbis and not to the Zonitidee. PLANORBIS COCKBURNI, n. sp. (Plate I. figs. 2, 2a, 2b.) Shell discoid, diaphanous ; sculpture, fine oblique striation, almost costulation, on the first whorls; colour pale horny brown; suture impressed ; whorls 2 | ; aperture broadly ovate. Size :- Major diam. 4*3, alt. axis 1*1 millim. 0*17, „ 0*04 inch. A large number of this species were found, associated with the last. I have named it after Lieut. Cockburn, of the 6th Royal Regiment, who accompanied Prof. Balfour and rendered him so much able assistance. HYDROBIA (?) BALFOURI, n. sp. (Plate I. figs. 4, 5.) Shell elongately oval; sculpture, quite smooth, a few eroded patches on the apical whorls ; colourwhite, another (smaller) specimen ash-brown ; spire high, somewhat attenuate ; whorls 5, penultimate the largest, its sides convex ; aperture subvertical, broadly ovate or nearly circular ; peristome thin, well rounded below ; operculum not seen. Size:- Major diam. 1*3, alt. apert. 0*9, alt. axis 2*1 millim » °"05' » °'H ,9 008 inch. ' |
