218 BULLID^. 



their dividing line well marked ; tlic last wliorl 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 



Fig^os. r^]j^y^^^ ^|jg 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 



B. Goui- curvature of the inner marp-in which is a little thickened, 



ail. ~ ' ' 



white, and polished. The outer lip, from its junction he- 

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

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

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

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



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

 hasset Rocks, and dredged Ijy 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 flat 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 ; Avhorls four, spire elevated, lip straight 

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



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



(1843). 

 Utriculus 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 



p. j.Qg distinct, as seen under the microscope ; spire elevated ; 



labrum 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. |^^, regioii ; 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 Bulla Gouldii, 

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



