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Show 738 LIEUT.-COL. GODWIN-AUSTEN AND MR. NEVILL ON [Dec. 2, its height, and almost circular, with the margins almost but not quite continuous, the columellar one being abruptly bent back over the umbilicus, and then beautifully and boldly rounded. I named this interesting little species after m y friend Mr. F. A. de Roepstorff, Dep. Sup. Andaman-I. Commission, to whom both the Museum at Copenhagen and myself are indebted for many interesting Mollusca and Coleoptera from the Andaman and Nicobar Islands (6?. N.). OPISTHOSTOMA PERAKENSIS, n. sp. (Plate LX, figs. 1, la, lb,) Shell dextral, much depressed, ovate, the last whorl reflected half a turn back and rising to a level with the penultimate suture ; colour ruddy brown; sculpture fine ribbing, wide apart and regular to the apex. Spire depressed, sides parallel, apex flat, suture deep. "Whorls 4, sides convex ; penultimate and antepenultimate equal, tbe last reversed. Aperture circular, vertical; peristome double, inner lip circular, continuous; the outer lip angular below. Size, alt. 0*30, major diam. 0*33 in. Perak. (Indian Museum, Calcutta.) Two examples of this very curious extremely minute shell were discovered by Mr. G. Nevill when washing out some of the larger specimens of the shells from the limestone caves, showing how often such delicate small species must be overlooked and lost by collectors (H. H. G.-A.). OPISTHOSTOMA PAULUCCLE, Crosse and Nevill, Journ. de Conchvliologie, t. xix. pp. 197 & 205 (1879), pi. viii. fig. 1. (Plate'LX. figs. 2, 2a, 2b.) Shell dextral, very depressed, ovate, the last whorl reflected more than a half turn backwards and rising to the top of the antepenultimate whorl; colour ruddy brown; the ribbing strong and wide on the last two whorls, very close and fine on those above. Spire depressed, sides parallel to axis, apex flat, suture moderately impressed. Whorls 4, penultimate and antepenultimate equal, their sides flat, the last whorl rounded and reversed. Aperture triangular, subvertical. Peristome double, both inner and outer lips. Size, alt. 0*30, major diam. 033 in. Perak. (Indian Museum, Calcutta.) This shell, a close ally in size and form of O. perakensis, presents a few characters by which it can be easily distinguished. I have, however, only seen one specimen, which was found in a similar way to that above described. Mr. Nevill informed me, before leaving for India, that this shell had been described by M . H. Crosse from a specimen he had sent him (G.-A.). DIPLOMMATINA CROSSEANA, n. sp. (Plate LX. figs. 3, 3a.) Shell dextral, elongately fusiform, sculpture widely and regularly costulate, colour pale sienna-brown ; spire gradually decreasing, suture moderately impressed. Whorls 7; antepenultimate the largest and most swollen ; penultimate short, from the last rising rapidly on it; constriction behind the aperture. Aperture rectangular, sub- |