254 MORCHIA. 



Subgenus Microtheca, A. Ad. 



Shell globosely turbinate, widely uuibilieate, somewhat porcel- 

 lauous, radiately rugosely plicate; sutures channelled; whorls 

 crenulate at the sutures. Aperture semicircular ; peritreme con- 

 tinuous ; inner lip thickened, arcuate ; outer lip with the margin 

 thickened ; umbilicus crenulate. Obs. These very peculiar little 

 shells are closely allied to Morchia, but the last whorl does not 

 embrace the others, as in that form, and the umbilicus is narrower 

 and crenulated at the margin. The outer lip also is varied. 



1. crenellifera (pi. 255, f. 41, 42), A. Ad. — Testa globoso- 

 turbinata, late umbilicata, alba, solida, semiopaca, longitudinali- 

 ter plicato-rugosa ; suturis canaliculars ; anfractibus ad suturas 

 crenulatis ; apertura subcirculari ; labio incrassato, arcuato ; um- 

 bilico margine crenato. Obs. In the general form and crenate 

 suture this curious little species resembles Isanda coronata, A. 

 Ad., which, however, on account of the polished porcellanous 

 character of the shell, 1 have referred to the family TJmbonidce. 



Subgenus Morchia, A. Ad. 



Shell obliquely ovate, depressed, widely umbilicated, convex 

 above, fiat beneath ; whorls rapidly increasing, the last dilated, 

 ascending, and embracing the other whorls as far as the apex. 

 Aperture oblong, oblique, somewhat horizontal, dilated below, 

 narrowed above; peritreme continuous, thickened. Obs. This 

 curious little genus resembles Teinostoma in the fact of the last 

 whorls embracing the others, but the base is not covered with 

 a callus, and the mouth is not anteriorly produced. 



1. obvoltjta (pi. 255, f. 43, 44), A. Ad. — Testa oblique 

 ovata, alba, depressa, late umbilicata ; anfractu ultimo ad peri- 

 pheriam angulato, striis incrementi confertis ornato, ad suturas 

 corrugato-crenulato ; umbilico patulo. Obs. This shell appears 

 to be rare in Japan. I only obtained two specimens; one at 

 Tsu-Sima, in 26 fathoms, and the other at Takano-Sima, in shell- 

 sand. It is a curious form, with an open umbilicus, and with the 

 last whorl encroaching upon and nearly covering the others, as it 

 does in Neritula and Teinostoma. 



Genus ADEORBIS, Searles Wood. 



Shell depressly conical-orbicular, deeply umbilicated ; whorls 

 flattened, spirally striated or smooth, the last more or less angu- 



