462 American Se ash ells 



2 to 2^4 inches in length, very elongate, moderately gaping at the bluntly 

 rounded, posterior end, and widely gaping at the foot end. Top margin 

 of shell folded back on itself at, and just anterior to, the beaks. No distinct 

 radial groove on the sides of the valves. Sculpture at anterior end is of prickly, 

 concentric lamellae which fade out toward the smoothish posterior third. 

 Siphon covered with a heavy, brown periostracum. May be dug out of 

 very soft shale at very low tides in a few localities. Moderately common. 

 Miss Turner advises me that this species must take the earlier name of Barnea 

 spathidata Deshayes. It was formerly known as B. pacifica Stearns. 



Genus Zirfaea Gray 1842 

 Zirfaea crispata Linne Great Piddock 



Figure 94c 



Newfoundland to New Jersey. Europe. 



1 to 2 inches in length, about half as high. Gaping at both ends. Charac- 

 terized by the radial, indented line which divides the valves into 2 areas: the 

 posterior section which has coarse, irregular growth lines, and the anterior 

 section which has fimbriated or scaled growth lines and a serrated edge. 

 A4oderately common in cold water where it burrows into soft r^ck. This is 

 the only member of the genus on the Atlantic Coast. 



Zirfaea pilsbryi Lowe Pacific Rough Piddock 



Bering Sea to San Diego, California. 



2 to 4 inches in length, gaping at both ends. Purportedly there are no 

 accessory plates present, except for a small mesoplax. The folded-back dorsal 

 margin at, and in front of, the beaks is covered with a thin, periostracal 

 membrane in fresh material. The yellowish periostracum at the posterior 

 end (siphonal end) is thin, but is not leaf-like as in Parapholas. No eggshell- 

 like material over the anterior foot gape. This species appears in old books 

 as gabbi Tryon. Dead specimens are commonly washed ashore. Siphon 

 studded with tiny, rounded flecks of chitinous material. 



Genus Pholas Linne 1758 

 Pholas ca77ipechiensis Gmelin Campeche Angel AVing 



Plate 32t 



North Carolina to the Gulf States and Central America. 



3 to 4 inches in length, Mj as high, fragile, purc-\\iiite and closely re- 

 sembling the False Angel Wing, Petricola pholadijonms, but lacking a 

 toothed hinge and ligament, and having a glossy plate rolled over the beaks 



