218 BULLIDiE. 



their dividing line well marked ; the last whorl is as long as the 

 shell, and includes all the others ; under the magnifier its surface 



appears covered with revolving lines ;. the whorls all rise to 

 ^'^' ^^' about the same level, so that the summit is nearly flat ; the 



anterior extremity is rather narrower than the posterior ; the 



aperture is narrow behind, and suddenly enlarged by the 

 ^•j^?"^- curvature of the inner margin, which is a little thickened, 



white, and polished. The outer lip, from its junction l)e- 

 hind, advances a little as it turns forward by a regular curve, and, 

 finally turning bacliward by a rather sharp turn, it joins the body 

 of the shell with a gentle twist ; umbilicus none. Length, three 

 tenths of an incli ; breadth, three twentieths of an inch. 



Found by Mr. Couthouy, in the stomachs of fishes taken off Co- 

 hasset Rocks, and dredged by Colonel Totten in Provincetown Har- 

 bor. Cape Cod, northward {Stimpson). 



In shape it somewhat resembles Bulla solitaria; but it is a smaller 

 and much more solid shell, and its fiat summit, with the display of 

 all its whorls there, plainly distinguishes it. The anterior extrem- 

 ity is also more pointed. It is much broader and less cylindrical 

 than U. canaliculatus, nor has it the conspicuous fold on the pillar, 

 as that shell has. 



Utriculus pertenuis. 



Shell minute, cylindrical, white, hyaline ; whorls four, spire elevated, lip straight 

 above, rounded below ; aperture narrow above, wide below. 



Bulla pertenuis, Mighels, Best. Proc. i. 129 (1843) ; Bost. Journ. iv. 346, pi. 16, fig. 3 



(1843). 

 Utriadus pertenuis, Stimpson, Check Lists, 4 (1860). 



Shell very small, cylindrical, of a dingy white color, very thin and 



fragile ; whorls four, rounded, all lying in the same plane ; suture 



J,, g^g distinct, as seen under tlie microscope ; spire elevated ; 



lal)rum nearly straight at the posterior part, rounded 



^ anteriorly, returning into the shell it forms a delicate, 



slightly elevated lamina, which, under the microscope, is 



seen to occupy nearly the whole length of the columel- 



. pertenuis. j^^, rcgiou ; apcrturc very narrow posteriorly, broad and 



rounded anteriorly. Length, eight one hundredths of an inch ; 



breadth, four one hundredths of an inch. 



When greatly magnified this shell resembles Bt/l/a Govldii, 

 Couth., but besides being much smaller, it is proportionally longer; 



