CANALIFERA. MOLLUSCA. PLEUROTOMA. 281 



below, and the elements concentric. Length ^^ inch, breadth ^^o 

 inch, divergence 48°. 



Found in the stomachs of fishes, not unfrequently. 



This is not liable to be confounded with any shell of our coast, ex- 

 cept Fusus harpularius, to which it has a miniature resemblance. But, 

 besides being so much smaller, it is distinguished by the notch at the 

 posterior angle of the aperture, and by the net-work formed by the 

 more numerous and fainter folds, and revolving lines. The color, 

 which Mr. Couthouy makes a distinctive mark, is very nearly the 

 same. His specimens were less perfect and white. In my freshest 

 specimen there is a broad, lighter-colored band near the top of the 

 lower whorl. Pleurotoma reticulata, Brown, (" Conchology of Great 

 Britain," &c., pi. 48, f, 29, 30,) may, perhaps, be intended to repre- ' 

 sent the same. 



Pleurotoma bicarina'ta. 



Shell ovate-fusiform, turreted, dusky-white ; whorls convex^ 

 with two revolving ribs, and other less conspicuous lines and 

 grooves ; notch of the lip shallow. 



Figure 186. 



State Coll., No. 273. Soc. Cab., No. 2365. 



Pleurotoma bicarinata, Couthouy ; Bost. Journ. JVat. Hist., ii. 104, pi. 1, f. 11. 



Shell small, tapering at both ends, turreted, of a dusky-white or 

 slate-color ; whorls six, convex, the lowest being half the length of 

 the shell, and marked with numerous, slightly elevated, revolving 

 lines, and smaller intervening ones ; about the middle is a deep 

 groove, on each side of which is a prominent revolving ridge or 

 keel, continued upon the upper whorls ; lines of growth very mi- 

 nute ; aperture elliptical, narrow, ending in a very short canal, 

 inclining a little to the left ; outer lip sharp, toothed by the re- 

 volving ribs, with a slight recess or notch at its posterior junction ; 

 pillar hp arched posteriorly. Length -f^ inch, breadth ^^ inch, 

 divergence 48°. 



First found by Mr. Couthouy in a fish caught off Nahant ; since 

 this single specimen, three or four others have been found by Dr. 

 Prescottj of Lynn, and Mr. W. W. Wheildon, of Charlestown. 

 36 



