MOLLUSCA OF THE ' CHALLEN&EE ' EXPEDITION. 603 



Inner lip — from the corner of the outer lip a very thin layer of 

 nacre spreads out a little way across the body, but then ceases 

 entirely. The pillar is spread out at its base as a confined, flat- 

 tened, unevenly inclined, semicircular, iridescent umbilical pad, 

 from the left corner of which the pillar proper projects, narrow- 

 edged but rounded, twisted, straight, bending to the left, and 

 advances into a sharply angulated, and, as seen from behind, even 

 mucronated junction with the basal mouth-edge, to which the 

 umbilical pad curving round the back of the pillar also attains. 

 The inside is scored with the external sculpture, and is bril- 

 liantly iridescent. The umbilical pad is defined by a narrow 

 furrow, and in front by a slightly tumid ridge, which is the least 

 nacreous part of the whole shell. Operculum is membranaceous, 

 horny, yellowish, with about six to seven turns, each strongly 

 defined by a narrow line of thickening, and sharply scored with 

 minute oblique radiating lines. H. 0'65. B. 0'87, least 0'7. 

 Penultimate whorl 0-199. Mouth, height 0-43, breadth 0-41. 



Unfortunately, though the operculum is preserved, nothing but 

 traces of the animal remain within the shell. 



Bembix, W., gen. nov. (/3e/i/3t^, a top.) 



Testa conica, alta, carinata, basi inflata, umbilicata, tenuis, margaritacea 

 epidermide tenui membranacea induta. 



The remarkable feature of this genus is its being covered with 

 a thin, extremely persistent, smooth, fibrous epidermis, like 

 that of some of the Helices, a feature to which I know nothing 

 similar in the family. The epidermis swells up and becomes pus- 

 tulated in water. In form the shell recalls some of the Cantha- 

 ridus group, but is thinner and on the base more tumid; the axis 

 is perforated, and the pillar is thin, reverted, and merely angu- 

 lated in front. It is very unfortunate that the shell, of which 

 there is but one specimen, is not quite full-grown, so that the form 

 of the umbilicus and, still more, of the mouth is very doubtful. 

 The animal, too, and the operculum are both absent. Its separa- 

 tion from the Turbonidse is thus not quite satisfactory. As to the 

 name of the genus, I think the only objection that can be taken 

 to it is that Philippi proposed the name Benibicium for one of the 

 genera of Litorinidse, but afterwards himself withdrew it for the 

 prior name of Sisella, Gray. 



1. Bembix -sola, W. 



St. 232. May 12, 1875. Mosima, Japan. Lat. 35° 11' JS"., 



