MARINE MOLLUSCA OF THE UNITED STATES. 95 



upon differences in the animals which do not appear to me to be 

 of generic value. 



1. P. c^cA, Miiller. Fig. 192. 



Zool. Danica, i. 45, t. 13, f. 1, 2, 3. 1788. 

 Patella Candida, Couthoiiy, Am. Journ. Science, xxxiv. 217. 1838. 



Shell small, conical, with numerous minute revolving ribs crossed 

 by fine concentric lines, giving the surface under the lens the ap- 

 pearance of network ; summit nearly central ; margin slightly 

 scolloped by the termination of the ribs. White. 



Length 8.75, height 2.5 mill. 



New England, nortJncards. {Eur.) 



2. P. TESTUDiNALis, Muller. Fig. 193. 



Prod. 237. 



Patella tessellata, Miill., Zool. Dan. Prodr., iii. 2868. 1788. 



Patella Clelandi, Sowerby, Trans, of Linn. Soc, viii. 621. \ 



Patella virginea, Mull., Zool. Dan. Prodr., iii. 2867, 1788. 



Patella amcena, Saj'-, Journ. Pliilad. Acad. ii. 223. 1822. 



Patella clypeus, Brown, Brit. Conch., t. 37, f. 9, 10. 1827. 



Lottia antillarum, Sowerby, Conch., Man. f. 231. 



Shell oblong-oval, frequently with a calcareous deposit, under 

 which we observe numerous radiating lines, which are crossed by 

 minute concentric wrinkles. Margin entire, acute ; apex behind 

 the middle, and turning towards the short end. Whitish or 

 greenish, with brown bands, frequently interrupted, forming 

 square tessellated spots; within bluish-white, etc., with an apicial 

 brown spot and marginal band. 



Length 20 to 38, width 12 to 20 mill. 



Northern Coast. {Europe.) 



3. P. ALVEUs, Conrad. Fig. 194. 



Journ. Philad. Acad., vi. 207, t. 11, f. 20. 1831. 



Shell oblong, sublinear, elevated, thin, pellucid, with fine radiat- 

 ing strise and fine concentric lines ; sides nearly straight ; apex 

 not central, pointing to the short end. Whitish, with reddish- 

 brown spots and lines, visible within. 



Length 1.5 to 12.5, width 5 to 7.5 mill. 



New England. 



This is doubtfully distinct from festudinalis. 



