40 



curved : cardinal teeth small and crowded ; series not much ar- 

 cuated; margin entire. Length \ an inch. 



P. corbuloides. Subtriangular, with one side cuneate and an- 

 gulated on the submargin; beaks central; cavity capacious; 

 margin entire. 



LUCINA. 



L. symmetrica. Shell lentiform, equilateral, thick, with regular 

 crowded and prominent acute concentric striae, and two or 

 three profound concentric sulci near the base : anterior side, 

 with a short submarginal muscular impression, profoundly 

 elongated. 



L. snbvexa. Shell suborbicular : ventricose ; with fine concen- 

 tric and minute obscure radiating lines ; posterior side with an 

 obscure fold, anterior side elevated and subangulated above; 

 hinge edentulous ; anterior muscular impression not profoundly 

 elongated : cavity very capacious ; surface punctate. 



L. pandata. Shell oval, compressed, obscurely cancellated ; 

 anterior side somewhat corrugated ; beaks nearly central ; teeth 

 three in one valve ; anterior muscular impression profoundly 

 elongated; lunule excavated, minute. Length li inches. 



Amer. Jour, of Sc. vol. 23. This shell is allied to Lucina 

 mutabilis, Lam. 



L. dolabra. Shell elevated, with distant concentric imbricated 

 and obscure radiating striae; posterior submargin profoundly 

 channeled, beaks prominent and cilrved forwards; lunule im- 

 pressed, cordate ; inner margin crenulated. Length half an inch. 



Amer. Jour, of Sc. vol. 23. 



L. alveata. Shell suborbicular, or rather elevated ventricose; 

 with two or three profound and numerous small concentric 

 sulci ; posterior end subtruncated ; posterior side with a submar- 

 ginal fold; beaks prominent; cardinal and lateral teeth distinct; 

 lunule minute, short, cordate, impressed ; margin minutely crenu- 

 lated. 



L. carinifera. Shell suborbicular, subequilateral ventricose, with 

 equidistant, acute, prominent concentric striae ; anterior side 

 with a profound fold, or obtuse elevation, and a cordate undulat- 

 ed depression ; posterior side with a profound indented fold, emar- 

 ginating the base ; anterior end emarginate above the fold ; beaks 

 prominent and incurved; cardinal and lateral teeth distinct; 

 cavity capacious ; margin crenulated. 



L. pomilia. Shell suborbicular, equilateral, obscurely cancel- 

 lated, with three or four profound concentric sulci ; and an in- 

 dented fold on both sides, terminating in an emargination of the 

 ends; beaks prominent, lunule profoundly impressed, cordate; 

 cardinal and lateral teeth very distinct : margin crenulated. 



[66J 



