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. 12, f. 1, 2, 3. 1788. 

 Patella Candida, Couthouy, 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, northwards. {Eur.) 



2. P. testtjdinalis, Miiller. Fig. 193. 



Prod. 237. 

 Patella tessellata, Mull., 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, Say, Journ. Philad. 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. 267, t. 11, f. 20. 1831. 



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

 ing striae 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 7.5 to 12.5, width 5 to 7.5 mill. 



New England. 



This is doubtfully distinct from testudinalis. 



