495 



costata, costis serratis, niargine ventrali Irevigato, rotiindato ; pos- 

 ticc prope medium conceiitrice striata, extremitate plus minusve at- 

 teiniata ; lamiuis tribus, una elongata ad margnnes ventrales, una 

 inter niargines dorsales, una magna, subquadrata, postice emargi- 

 nata, super umbones posita. 



An enclosed species, with the dorsal part of the anterior ribbed 

 angularly by raised, serrated ridges. The posterior portion is con- 

 centrically striated, and at the termination indeiinitely extended. 

 There is a thin, long plate between the dorsal margins, and another 

 over the ventral margins. The umbonal shield is large, rather 

 ([uadrate, and at the posterior edge emarginated. 



I'ound on the coasts of Great Britain, and in floating wood in 

 various parts of the Atlantic. Mr. Cuming has collected varieties 

 at the Pliilippine Islands. 



80. Pholas cuneiformis (pi. civ. f. 38,39, pi. crai. f. 86,87), 

 Say, Journ. Ac. Sci. Philad. vol. ii. p. 322. 



Ph. testa oblonga, clausa, transverse oblique divisa ; antice mar- 

 gine ventrali Isevigato, rotundato, latere dorsali costis longitudina- 

 libus arcuatis, serratis ; postice concentrice striata, plus minusve 

 attenuata; laminis tribus, una elongata ad margines ventrales, 

 una inter margines dorsales, una ad umbones antice obtuse angu- 

 lata, postice acuminata. 



Resembling FL striata (f. 40, 41, 42, 43, 44), but with the 

 striae, or ribs, of the anterior part curved, not angular, and the 

 dorsal sliield smaller, and pointed at each end. 



N. America. 



31, Pholas semicostata (pi, cviii. f. 84, 85), {copied), Lea, 

 Pro, Best. See. Nat. Hist,, Nov, 1814, pi, 24, f. 1. 



Ph. testa Ph. cuneiformi simiUima, sed magis pyriformi ; laminis 

 marginalibus nulHs ? 



This may possibly may be identical with Ph. cuneiformis, or 

 with Ph. striata, but it is more ventricose, and no marginal plates 

 are mentioned in the description. 



It is a very small shell, inhabiting the coasts of South Carolina. 



32. Pholas corticaria (pi. cviii. f. 94, 95, 96), Gray, MS. 

 Brit. Mus. 



Ph. testa clausa, divisa; antice angulatim longitudinaliter costata, 

 costis serratis, margine ventrali lievigato ; postice prope medium 



3 s 2 



