258 TK1N0ST0MA. 



Obs. A small thin depressed species, very shining and with con- 

 vex whorls ; the margin of the umbilicus is not carinate. 



18. carinata (pi. 256, f. 18, 19), A. Ad. — Testa ovato-orbi- 

 cularis, obliqua, depresso-conoidalis, subdiaphana, alba, late um- 

 bilicata; aufractibus convexiusculis, transverse tenuiter striatis, 

 rapide accrescentibus, ultimo antice dilatato, ad peripheriam acute 

 cariuato ; apertura subtrigonali, antice angulata et producta ; um- 

 bilico margine acuto. Obs. The keel at the periphery is marked 

 and prominent, forming an acute ledge round the last whorl. 

 The only other species at all resembling it is A. subcarinata, 

 found in the British seas. 



19. trochula (pi. 256, f. 12, 13), A. Ad. — Testa orbicularis, 

 depresso-conoidea, profunde umbilicata, supra convexa, infra 

 plana, alba, semipellucida ; aufractibus 5|, planiusculis, lente ac- 

 crescentibus, suturis marginatis ; anfractu ultimo antice vix dila- 

 tato, ad peripheriam obtuse angulato ; apertura subangulata, 

 antice vix producta; umbilico margine acuto. Obs. This species 

 resembles a small depressed TrocJivs, with a flat base, a some- 

 what angular periphery, and a deep, rather narrow umbilicus. 



20. subangulata (pi. 256, f. 33, 3±), A. Ad.— Testa ovato- 

 orbicularis, subdepressa; vertice elatiusculo ; alba, radiatim tenuiter 

 striata, profunde umbilicata ; anfractibus 3|, convexiusculis, ul- 

 timo antice dilatato, superne obtuse angulato, infra subplano ; 

 apertura subquadrata, antice producta; labro supra subangulato ; 

 umbilico margine acuto. Obs. The angular projection of the 

 whorls is not at the periphery but above it, which causes the 

 subquadrate form of the aperture ; whereas in the British A. sub- 

 carinata and the Japanese A. carinata the periphery is carinate, 

 more or less, and the aperture triangular. 



21. diaphana (pi. 256, f. 39, 40), A. Ad.— Testa depresso- 

 orbicularis, alba, tenuis, pellucida, late et profunde umbilicata; 

 spira prominula; anfractibus ?>\, subplanulatis, lineis incrementi 

 ornatis ; anfractu ultimo antice vix dilatato, ad peripheriam rotun- 

 dato ; apertura circulari ; umbilico patulo, perspectivo, margine 

 cariuato. Obs. This little pellucid shell is more globose than 

 the species of Adeorbis generally, and the aperture is nearly cir- 

 cular, with a continuous peritreme. 



Genus TEINOSTOMA, A. Ad. 



Shell with the spire depressed, polished or spirally sculptured ; 

 whorls rapidly increasing, umbilical region callous. Aperture 



