TURBINACEA. MOLLUSCA. LITTORINA. 259 



dusky streak on the outside. If so, we should have another decisive 

 distinguishing mark. 



After long and careful observation and study of the myriads of speci- 

 mens on our shores, so infinitely varied in proportions, coloring, and 

 sculpture, I have become satisfied in my own mind, to what species 

 they should be referred. The limits of the species too, in adult speci- 

 mens, are decidedly marked both by the shells themselves and by 

 the animals. But, as to the young, to use the language of Montagu, 

 " the shades and gradations are so intimately blended, that it is scarce 

 possible to determine what marks a characteristic line of division." 

 The angle of the front I regard as the most constant character of the 

 last species. 



It seems almost incredible that Mr. Say should have drawn upon the 

 State of Maine for specimens of shells, which are so extensively dis- 

 tributed, and so innumerable with us; and still more incredible, that, 

 fr'om the few specimens which he probably received, he should have 

 discriminated and described the thi'ee species so accurately, though, if 

 my conclusions are correct, some of them were previously described. 



LiTTORl'NA TENEBRO'SA. 



Shell ovate-conical ; spire elevated, whorls tumid, with numerous 

 revolving lines, dark-green or duslcy-hroion, with interrupted 

 cream-colored lines ; aperture circular; purplish-chocolate ivithin. 



Figure 166. 



State Coll., No. 3S. Soc. Cab., No. 879. 



Turbo tenebrosus, Montagu ; Test. Brit., 303, t. 20, f. 4. Maton and Rackett ; 

 Lin. Trans., viii. IGO, Dillwyn ; CateZ., ii. 818. Tdrton; Conch. Diet., 197, 

 f. 36, 37. Brown ; Conch, of Great Brit., <^c. Fleming ; Brit. Jlnim., 298. 



Turbo vestitus. Say ; Journ. Acad. JVut. Sc, ii. 241. 



Shell small, ovate-conical, rather thin, dark-olive or dusky- 

 brown, usually prettily checkered with bufF-colored, broken lines, 

 generally obscured by a gray or rusty coating ; spire elevated and 

 pointed, of five or six rounded, tumid whorls, marked with ob- 

 scure revolving lines ; suture well defined ; lower whorl two 

 thirds the length of the shell ; aperture less than one half, nearly 

 circular ; outer lip thin and sharp, yellowish, thickening a little as 

 it meets the flattened and slightly everted pillar lip, forming a 



