278 TROCHID^. 



Family TROCIIIDyE. 



Shell tnrreted or conoid ; aperture rounded or oblong, not spread- 

 ing ; lips disunited posteriorly. 



Ocniis AOEORBIS, Searles Wood. 1842. 



Shell dcpressly 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 costulata, Moller, Ind. Moll. Gr. 8. 



Adeorbis costulata, Stimpson, Proc. Bost. See. 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 ajjpearing to 

 advaiitaoe only on the thinner and more delicate outer 

 whorl, which is convex, rounded, and covered with 

 f. prominent, crowded ribs. On the side of the whorl 

 many of these ribs divide into two, thus occupying the 

 A. costulata. jj^c^eased space ; and beneath, the ribs flow into each 

 other and gradually disappear without interrupting the five distant, 

 elevated, spiral strias on the nmljilical half of the base. The umbil- 

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

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

 which the outermost are testaceous, presenting a frosted apjjcar- 

 ance ; the central volutions, occupying about one fourtli of the diam- 

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

 (IF. Sliinpson). 



Ociiiis ITIARGARITA, Leach. 1819. 



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

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

 operculum multi-spiral ; the nucleus central. 



