38 



PHOLADID^. 



Fig. 364. 



Pholas truncata. 



Shell white, oblong, beaks at anterior third, anterior portion triangular, acutely 

 pointed, posterior end broadly truncate ; surface with coarse lines of growth and 

 radiating riblets, denticulate in front, simple posteriorly, dorsal shield single, lan- 

 ceolate, grooved along the centre. 



Pholas truncata, Sat, Journ. Ac. Nat. So. ii. 321 (1822). — De Kay, Moll, of New York, 

 248, pi. 34, fig. 223«, 6. — Gould, Proc. B. S. N. H. ii. 81. — Stimpson, Shells of 

 New England, 25. — Sowekby, Thes. Conch, ii. 488. t. 104, figs. 29, 30. — Hanley, 

 Descr. Catal. 6, pi. 9, fig. .56. — L. 11. Gibbes, Fanna of So. Car. in Toumey's Geol. 

 of So. Car., Append, xxii. — Fischer, Journ. Conch. 2d ser. iii. 48. — Gray, Ann. 

 and Mag. Nat. Hist. 2d ser. viii. 381. — Jay, Catal. 4th ed. 10. — Kurtz, Catal. 

 SheUs of No. and So. Car. 3. — Tryon, Proc. Ac. Nat. Sc. xiii. 202 (1862). 



Shell chalky white, oblong, with prominent lines of growth, and 

 radiating ril)lcts, excepting at the upper anterior margin, and a pos- 

 terior superior triangle on which there is a thin straw-colored epi- 

 dermis, which extends beyond 

 the end in a long sheath ; 

 the anterior riblets sharply 

 toothed as they cross the con- 

 centric ridges ; beaks at an- 

 terior third ; anterior portion 

 triangular, acutely pointed, 

 the lower margin concavely 

 arched, the upper margin roll- 

 ing outward, near the beaks, 

 the ventral face with a large oval opening ; posterior portion oblong, 

 squarely truncate at the end so that the margins are nearly parallel, 

 dorsal margin gradually opening to the end, which is entirely open. 

 Interior smooth : rib short, rounded at insertion, a little flattened 

 towards point, accessory valve lanceolate, square at beaks with a 

 portion bent downwards, pointed in front, grooved along the middle 

 with lines of growth converging to it. 



Length, three inches ; height, one and one half inches ; breadth, 

 one and one fourth inches. 



Found at New Bedford at the end of Long Wharf, in two feet 

 mud, with P. costata, by Thomas A. Greene, Esq. It was not pre- 

 viously known this side of Carolina, where Mr. Say found it, and 

 where it is of much smaller size. It has since been found in Long 

 Island Sound and New Jersey. 



It is much more delicate than P. crispata, the margins of tlic 

 hinder portion much more nearly parallel ; there is no furrow 



p. truncata. 



