220 BULLID^. 



and at the umbilical region it enters the shell and forms a conspicuous fold. Length, 

 seven fortieths of an inch ; breadth, four fortieths of an inch. 



Found on Chelsea Beach hy myself, at Provincetown by Colonel Totten, at New Bed- 

 ford by Professor Adams, and is not unfreqaently taken from fishes. 



The same remarks which were made under the preceding species, as to its generic 

 place, apply to this species. 



This shell closely resomhles the figures, and agrees in general with the description, of 

 Bulla obtnsa, of Mon'agu ; but in neither of them is any fold at the base of the pillar 

 noted, and our shell has a more elevated spire, and wants tlie consjncuous lines of growth 

 which peculiarly mark the British shell. B. canaliculuta differs in its more slender, cylin- 

 drical, and smooth appearance, the broad and shallow groove of the whorls, its very acute 

 summit, and its more slightly plaiied pillar-lip. In adult specimens it is easy to discrim- 

 inate the two species ; but the half-grown specimens are so ncarl_v alike as to render it 

 almost impossible to separate them. Mr. Lea describes and figures a fossil species in his 

 " Contributions to Geology " under the name of Aclceon WelherllU, which must very 

 closely agree with this shell. 



Oeiiiis CYLICHIVA, Loven. 1846. 



Tentacular lobes connate, indistinct; eyes sessile on their front 

 bases. Mantle with a tliick, posterior lobe, partially closing the 

 aperture of the shell. 



Shell solid, cylindrical, involute ; spire none, apex obtuse, umbil- 

 icated ; aperture narrow and linear, as long as the body whorl ; in- 

 ner lip callous, with a single anterior fold ; outer lip straight, simple. 



Cyliclina alba. 



Fig. 98. 



Shell cylindrical, smooth, whitish, of the size of a grain of rice, a pit in place 

 of the spire. 



Volmria alba, Browx, Conch, iii. 3. 



Bulla tritieea, CouTiiouY, Bost. Joiirn. Nat. Hist. ii. 88, pi. 2, fig. 8 (18.?8) ; Sillim. 



Journ. Old Series, xxxiv. 217 (18.38).— Gould, Inv. 165, fig. 98. — Ue IUy, N. Y. 



Moll. 17, pi. .35, fig. 326. 

 Bulla corticata, Moller, Ind. Gr. 6. 

 Cyliclina alba, Stimpsox, Check Lists, 4. 



Shell cylindrical, polished, rather solid, of a dull white color, and 

 covered with a thin, rusty epidermis ; marks of growth very del- 

 icate, and numerous minute revolving lines may be seen un- 

 der a magnifier ; a circular pit occupies the region of the 

 spire, from the margin of which the outer lip takes its origin, 

 and, rising a little, passes forward in a direction nearly paral- 

 c.aiba. j^^ ^^^ ^^^^ j^^^ margin of the shell, forming a long, narrow 



aperture, which suddenly becomes double this breadth, near the 



