278 TEOCHID^. 



Family TROCHID^. 



Shell turreted or conoid ; a})erture rounded or oblong, not spread- 

 ing ; lips disunited posteriorly. 



Ociiiis ADEORBIS, Searles Wood. 1842. 



Shell dcprcssly conical, orbicular, deeply umbilicated ; whorls 

 few, not nacreous, flattened, smooth or striated, the last more or 

 less angulated at the periphery ; aperture transversely oval, peris- 

 tome interrupted ; inner lip sinuated, outer lip arcuate, simple, 

 acute. 



Adeorbis costulata. 



Margarita cotitiilatn, Moller, Ind. Moll. Gr. 8. 



Adeorbis costulata, IStimpson, Proc. Bost. Soc. iv, 14 (1851) ; Shells of New England, 32; 

 Check Lists, 4. 



It is minute, about one tenth of an inch in diameter, white, some- 

 what thick and rugged near the apex, the sculpture apjiearing to 

 advantage only on the thinner and more delicate outer 

 whorl, which is convex, rounded, and covered with 

 prominent, crowded ribs. On the side of the whorl 

 many of these ribs divide into two, thus occupying the 

 . costu a a. jj^d'eased space ; and beneath, the ribs flow into each 

 other and gradually disappear without intcrru])ting the five distant, 

 elevated, spiral striie on the umbilical half of the base. The umbil- 

 icus is deep. The aperture is rounded, with the peristome contin- 

 uous. The operculum is multispiral, of about eiglit volutions, of 

 which the outermost are testaceous, presenting a frosted appear- 

 ance ; the central volutions, occu|)yiiig about one fourth of the diam- 

 eter, are corneous. In deep water off Cape Ann, Grand Manan 

 ( W. Stimpsori). 



Ociiiis MARGARITA, Le.^ch. LS19. 



Shell conical, moderately elevated ; whorls few, sub-inflated ; 

 aperture rounded, imperfect posteriorly; lip sharp; umbilicus deep; 

 operculum nmlti-spiral ; the nucleus central. 



