PHOLADARIA. MOLLUSCA. PHOLAS. 27 



Pholas costata. 



Shell large, oblong-ovate, white, covered with radiating, toothed 

 ribs. 



State Coll., No. 246. Soc. Cab., No. 1702. 



Pholas costatus, Lin.; Syst. J\''at., 1111. Lister; Conch., pi. 434. Gualt. ; 

 Test., t. 105, f. G. Chemn. ; Conch., viii. t. 101, f. 863. Brug. ; Encyc. 

 J>/^tA., pi. 109, f. 1, 2. Blainville ; JI/a?ac<;Z., pi. 99, f. 6. Sowerby ; Genera, 

 No. 23, pi. 1. Lam. ; An. sans Vert., vi. 45. Wood ; Gen. Conch., pi. 15, 

 f. 1, 2. Index, pi. 2, f. 4. 



Shell large, thin, inflated, oblong-ovate, rounded before and 

 narrowed behind, white, covered with radiating ribs, the coarse 

 lines of growth rising over them in an undulating manner, so as to 

 produce tooth-like elevations upon them, at regular intervals ; the 

 interior is marked with corresponding indentations. Length G 

 inches, height 2 inches. 



This well known species is admitted into our catalogue from the 

 fact, that Professor Adams has lately discovered an extensive bed of 

 dead shells at New Bedford. It probably is not to be found in a liv- 

 ing state in our waters. Indeed, I am not aware that it is found livina; 

 on the shores of any of the Middle or Eastern States. It is found, in 

 the above locality, of all sizes and ages, its most delicate portions 

 entire, forbidding the idea that these shells were transported by any 

 means from some distant locality. It is certainly remarkable, that a 

 large shell should have been abundant at no very distani period, which 

 cannot now be found living within one or two thousand miles. Some- 

 thing of the same kind is said to belong to the history of the oyster 

 about Cape Cod. 



Pholas crispata. 



Valves touching at the middle of the base, and widely gaping at 

 both sides ; a furrow passes from the beaks across the middle, in 

 front of which are radiating, toothed ribs. 



State Coll., No. 247. Soc. Cab., No. 2316. 



Pholas crispata, Lin.; Syst. JVat., p. llll. Gmelin ; Syst., p. 3216. Pennant; 

 Brit. Zool., iv. 157, t. 43, f. 2. Montagu ; Test. Brit., 23. Donovan ; Brit. 

 Shells, ii. pi. 62, 69. Chemn.; viii. 369, t. 102, f. 872-874. Tdrton ; Brit. 

 Biv., 6. Conch. Diet., 14G. Lin. Trans., viii. 32. Hutch., Dorset Catal., 



