154 INVERTEBRATA OF MASSACHUSETTS. 



Shell oblong-oval, moderately elevated, thin ; apex behind the 

 middle, pointed, and turning forwards ; surface finely checkered 

 with minute radiating lines crossed by encircling lines ; general 

 color a greenish-white, with dark-brown stripes radiating from the 

 summit, and frequently dividing, before they reach the margin, 

 which is sharp and entire ; within, the central portion is dark- 

 brown, and the margin is more of less bordered or checkered 

 with the same color, by the exterior markings showing through. 

 Ordinary length inch, breadth |- inch, height \ inch. 



Found along our whole coast, adhering to the rocks, and is com- 

 mon on the northernmost shores of Europe and America. 



This shell varies infinitely in its markings. The general appear- 

 ance is as above described. Sometimes, all exterior coloring is want- 

 ing ; and commonly, the lines are so delicate, and arranged in such a 

 manner, as to exhibit a kind of net-work. The largest specimens I 

 have seen were brought from Castine, Maine. These were 1 inch 

 in length. There can no longer be any doubt that this is the shell 

 long known in the North of Europe as P. testudinalis. Specimens 

 sent me from Ireland, Scotland, and Norway, agree in every par- 

 ticular with ours. Probably the P. Antillarum is the same, though 

 Mr. Sowerby does not intimate this in his correspondence. 



Mr. Couthouy was the first to determine the generic place of this 

 shell, by an inspection of the animal. 



I have employed the generic term LOTTIA, of Gray, as it has the 

 right of priority, is not an objectionable derivative, and is in general 

 use among all conchologists except the French. PATELLOIDEA was 

 also given, as the name of a family, by Blainville. The arrangement 

 of the branchiae of the animal would, strictly, remove the genus from 

 this family. 



LOTTIA ALVEUS. 



Shell oblong-oval, compressed at the sides, thin, colored with a 

 net-work of white and brown. 



FIGURE 13. 



State Coll., No. 130. Soc. Cab., No. 777. 



Patella alveus, CONRAD ; Journ. Acad. Nat. Sc., vi. 267, pi. 11, f. 20. 

 Patelloidea alveus, COUTHOUV ; Bost. Journ. Nat. Hist., ii. 177. 



