lOQ JOURNAL OF THE NEW JERSEY 



1. Dosinia discus, Reeve. Shell nearly round, compressed, with 

 five, regular, impressed, concentric lines ; umbones quite sharply 

 pointed ; lunule cordate, slightly impressed ; hinge with a large, 

 oblong groove under the umbones ; muscular impressions very 

 large ; pallial sinus deep, ascending. Epidermis yellowish-white. 

 L. 66 ; H. 61 : \V. 22 ; U. nearly J.— Virginia and south. 

 Family 17. PETRICOLID/E. 



Represented only by the genus: — 



1. Petricola, Lam. 



Shell oval or elongated, thin, tumid ; umbones near anterior 

 end ; hinge with 2 or 3 teeth in each valve ; pallial sinus deep. 



1. Petricola j^holadifonnis, hdim. (Fig. 15.) Shell oblong-ellip- 

 tical, swollen, gaping, with a distinct, ovate lunule on the short 

 (anterior) end, and a moderate, projecting, external ligament on 

 the long end ; hinge with two teeth in each valve ; pallial sinus 

 deep, horizontal ; surface covered with elevated, radiating lines ; 

 7 or 8 of the front ones are distant, coarse, and toothed ; back of 

 these, they are much closer, finer, and but slightly roughened by 

 the distinct lines of growth ; interior with radiating furrows. 

 Chalky white. L. 32 ; H. 14 ; W. 11 ; U. h, often larger. 



Animal with mantle united except for the siphons and foot ; 

 siphons long, slender, separated, except at base, the lower one 

 fringed; foot triangular, long and narrow. — Common south of 

 Cape Cod, rare north. Boring in clay. 



Family 18. DONACID/E. 

 Shell closed, triangular-wedge-shaped, usually thick; liga- 

 ment short external; cardinal teeth two in each valve; pallial 

 sinus deep, horizontal. Animal with fringed mantle and short 

 separated siphons. 



1. DONAX, L. 



Shell trigonal, wedge shaped, closed ; front rounded, back 

 pointed ; ligament external ; pallial sinus deep. 



Animal with fringed mantle and short, thick, diverging si- 

 phon ; foot very large. 



1. Donacc/ossor, Say. (Figs. 12-14.) Shell triangular wedge- 

 shaped, closed ; anterior end elongated, rounded ; the hinge slope 

 straight to the tip ; posterior end obliquely rounded, very short, 

 external ligament very short, prominent, on the shorter end of 



