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Show 342 LIEUT.-COL. H. H. G O D W I N - A U S T E N O N [June 18, RHIOSTOMA, Benson. 26. R H I O S T O M A C A V E R N S , n. sp. (Plate X X X V I . figs. 1, la.) Shell dextral, discoid, rather solid, very widely and perspectively umbilicated ; sculpture smooth, with fine transverse lines of growth ; colour pale umber-brown ; spire just raised above last whorl: apex flat; suture well impressed ; whorls 4, well rounded, the last separated from the others for a distance of 4 millim., the sutural tube lying about midway, rather nearer to the aperture, it is short and recurved ; aperture circular, oblique; peristome double, inner simple, continuous, the outer expanded on the exterior margin and into a very slight wing at the sutural side. Size: maj. diam. 15-0, min. 10*5; alt. axis 3*25; diam. body-whorl 6 0 millim. Operculum multispiral, shelly in front and slightly convex, double, horny, polished, multispiral at inner side. Hab. Sarawak proper. The first specimens sent home by Mr. Everett were four in number, obtained when making excavations in certain caves in the limestone formation, and marked Cave A. The specific name is only given in allusion to this work, not that the species habitually lives in such places. These are somewhat larger than the one described and figured, being in major diam. 19 millim., minor diam. 14 millim. 27. RHIOSTOMA GWENDOLENS, n. sp. (Plate XXXVI. figs. 2, 2a.) Shell dextral, globosely discoid, solid, openly umbilicated; sculpture a thick finely striate epidermis ; colour dark umber-brown, with transverse bands of a darker colour, towards the apex zigzag bars are seen where this epidermis has come off; spire low ; apex papilli-form ; suture well impressed ; sutural tube 2 millim. in length, tapering and directed forward ; whorls 4\, rounded, the last separated from the other whorls from the base of sutural tube; aperture circular ; peristome double, the inner lip thin and continuous, the outer expanded and reflected on the outer margin. Size: maj. diam. 15*25, min. 11*75; alt. axis 5*0; diam. body-whorl 7*5 millim. Operculum thin, flat, smooth, multispiral, and shelly in front, smooth and horny behind, with a central circular hole. Hab. Niah Hills (A. Everett). Only one specimen in the collection, which is quite distinct from all other species of this genus from Borneo in its more closely round and globose form. 28. RHIOSTOMA HUNGERFORDI, n. sp. Shell discoid, umbilicated ; colour rich dark madder-brown, crossed with broad regular V-shaped markings for 4 whorls, where the varix of an old aperture is seen; in front of this the markings are less developed ; spire perfectly flat; apex papillate, scarcely raised above the succeeding whorls ; suture well impressed, the tube small, adhering |
