168 INVERTEBRATA OF MASSACHUSETTS. 



vated spire, and wants the conspicuous lines of growth which pecu- 

 liarly mark the British shell. B. canaliciilata differs in its more slen- 

 der, cylindrical, and smooth appearance, the broad and shallow groove 

 of the whorls, its very acute summit, and its more slightly plaited pil- 

 lar-lip. In adult specimens it is easy to discriminate the two species ; 

 but the half grown specimens are so nearly 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 AclcBon WelheriUi, which must very closely agree with this 

 shell. 



Bulla oryza. 



Shell minute, white, glossy, sub-oval, last tvhorl enveloping all 

 the others, and marked with a few revolving lines ; summit c?e- 

 pressed, imperforate. 



Figure 93. 

 State Coll., No. 120. Soc. Cab., No. 2387. 



Bulla ory^za, Totten ; Sillimaii's Journ., xxviii. 350, f. 5. 



Shell not very small, not very thin, translucent, white, regularly 

 diminishing from the middle towards each end, the tip being de- 

 pressed into a shallow pit, and the front being rather pointed ; last 

 whorl enclosing all the others ; surface marked with minute lines 

 of growth, a few revolving lines on the anterior portion, and a few 

 more obscure ones near the shoulder, none of them perceptible 

 without a magnifier. Aperture as long as the shell, narrow be- 

 hind, and widening forwards ; outer lip simple and sharp, com- 

 mencing beyond the axis of the shell, and rising a little, then 

 turns, and passes forwards by a regular curve ; the left margin is 

 thickened, and forms a smooth, glossy pillar, which is twisted so 

 as to form an oblifpie fold ; at tiie base it terminates abruptly, so as 

 almost to form an obtuse tooth ; a thick callus, commencing at 

 the junction of the outer lip, runs round within the whorl, giving 

 strength to the region of the spire. There is no umbilical open- 

 ing either at the tip or base. Length 2^^ inch, breadth y^ inch. 



Found by Professor Adams in the mud of New Bedford har- 

 bour. It was originally found by Colonel Totten in the harbour 

 of Newport. It seems not to have passed Cape Cod. 



