806 LITTORINIDiE. 



it differs in its less elongated spire, its larger aperture, encircled as 

 it were by a broad, thick, fattened rim. 



I have not seen the animal, but Montagu says it is yellowish, 

 without stripes or spots ; the tentacula of the same color, marked 

 with a 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 

 specimens on our shores, so infinitely varied in proportions, color- 

 ing, and sculjjture, I have become satisfied in my own mind to what 

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

 adult specimens, 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 possiljle to determine what marks a characteristic 

 line of division." The angle of the front 1 regard as the most con- 

 stant 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 

 distributed and so innumerable with us ; and still more incredible 

 that, from the few specimens which he probably received, he should 

 have discriminated and described the three species so accurately, 

 though, if my conclusions are correct, some of them were previously 

 described. 



Littorina tenebrosa. 



Fig. 166. 



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

 lines, dark green or dusky brown, with interrupted cream-colored lines ; aper- 

 ture circular; purplish-chocolate within. 



Turbo tenrhmsits, Montagu, Test. Brit. 303, t. 20, %. 4. — Wood, Ind. pi. 30, fio;. 6.— 



Maton and Rackett, Lin. Trans, viii. ICO, jtl. 4, fig-. 12. — Dillwyx, Catal. ii. 



818. — TiRTON, Conch. Diet. 197, figs. 36, 37. — Bkown, Conch, of Great Brit. &c. 



— Fleming, Brit. Anim. 298. 

 Turbo vfstitus, Say, Journ. Acad. Nat. So. ii. 241 ; ed Binney, 82. 

 Littorina tenebrosa, GouLD, Inv. 1st ed. 259, fig. 166. — De Kay, N. Y. JMoll. 105, pi. 6, 



fig. 106. 

 Littorina ritilis, part, Stimpson, Shells of New England, 33 



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

 usually prettily checkered with Iniff-colored broken lines, generally 

 obscured by a gray or rusty coating ; spire elevated and pointed, 

 of five or six rounded, tumid whorls, marked with ol)Scure revolv- 

 uig lines ; suture well defined ; lower whorl two thirds the lengtli 



