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 ot 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 the 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 ( Palseontologia Indica, plate i. 

 figs. 8, 8 «, 8 b, p. 12). The latter is represented as a dextral shell 

 with flat-sided whorls angulate above ar,:! below. And if the two shells 

 are compared in this position, it will be 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 Zonitidse. 



Planorbis cockburni, u. sp. (Plate I. figs. 2, 2a, 26.) 



Shell discoid, diaphanous ; sculpture, fine oblique striation, almost 

 costulation, on the first whorls ; colour pale horny brown ; suture 

 impressed ; whorls 2g ; 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. 1 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, sonicwhat 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. 

 .. 0-05, „ 0-04, „ 008 inch. 



