37 



PETRICOLA PHOLADIFORMIS. 



Tab. VII, Jig. 3. 



^ SPECIFIC CHARACTER. 



Shell elongated, anterior side short, with strong 

 ribs crossed by waved striae ; posterior side with ra- 

 diating lines, and gaping; teeth three in one valve, 

 and two in the other. 



SYNONYME. 



Petricola PHOLADIFORMIS, Lum. An. sans vert. 

 vol. 5, p. 5^5. 



Sowerby^s Genera, JVb. XV, pi. 1, Jig. 1. 

 Petricola fornicata, Say, Journ. Acad. JsTat. 

 k "^flk^r Sciences, vol. 2, p. 319. 



Cabinet of the Acad. Nat. Sciences, No. 860. 

 observations. 



This shell is irregular in form, and marked with 

 strong indented lines within on the anterior side. 

 The hinge teeth, when perfect, are invariably three 

 in one valve, the middle tooth being the largest and 

 bifid; on the opposite valve are two bifid teeth. 



A very common species on all parts of the coast, 

 at least as far north as Maine. Mr. W. R. Clapp in- 

 forms me that it is gregarious on the shore of Long 

 Island Sound, in company v,ith Pholas truncata, 



E 



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