174 NEW-YORK FAUNA — MOLLUSCA. 



on both sides near the hinge. Surface with numerous imbricated striae radiating from the 

 beaks, with a few distant concentric striae, which, in old age, become deep sinuous furrows, 

 the radiating stria? becoming obsolete. Beaks small, distinct, contiguous. Hinge-margin 

 straight : ligament inserted into a sublinear pit, black, greyish on the sides nearest the base 

 of the pit; within smooth, polished. Muscular impression distinct. 



Color. Convex valve pale reddish (on the beaks reddish brown), with pale radiating lines 

 and deeper red concentric circles ; lower valve yellowish or tinged with reddish ; within 

 polished white. 



Length, 4 • - 5 ' 0. Width, 4 • 5 - 5 • 5. 



The plate represents the upper valve of a moderate sized shell : the old shells are frequently 

 eroded and pierced by other marine animals. Specimens have been taken by dredging in 

 deep water off Sandyhook, where it appears to be not uncommon, as many were taken at 

 the same time. 1 have also obtained them in fifteen fathom water, on the south coast of 

 Long island : the convex valves were all more or less deeply sculptured and eroded by marine 

 parasites. They are represented to be palatable as food. 



{EXTRA-L1MITAL.) 



P. purpuralus, Lam. (P. dislocatus, Say, Ac. Sc. Vol. 2, p. 260 ; Am. Conch, pi. 56, fig. 2. Con- 

 rad, Am. Mar. Conch, p. 10, pi. 2, fig. 2.) Shell suborbicular, with 20 - 22 elevated rounded 

 ribs and numerous concentric wrinkles : no longitudinal strias ; ears subequal ; hinge margin 

 straight in each valve. Color, whitish tinged with yellow or reddish, with a few narrow transverse 

 interrupted and dislocated reddish undulated lines, and 5-6 obscure spots on the margin at the base 

 of the ears. Length, 1-5 -2*0; width, l-6-2 - 2. Southern coast. 



P. ornatus, Lam. (Conrad, Mar. Conch, pi. 2, fig. 3.) Shell small, somewhat longer than broad, 

 subequivalve, compressed : ribs 30 - 36, alternately smaller and subscabrous ; one of the ears very 

 small. Color, pale yellowish, with red angular spots. Length, 1-5: width, 1-3. Florida. 



P. nodosus, Lam. (Conrad, ib. pi. 2, fig. 2.) Shell with nine thick rounded ribs, and strong 

 radiating striae ; ribs with large hollow vesicles. Color, reddish brown, orange or white. 

 Length and breadth, 2-0- 5 - 0. Florida. 



P.varius. (Turton, Conch. Ins. Brit. p. 214.) Shell oblong, nearly equivalve, with from twenty- 

 five to thirty compressed ribs more or less clothed with concave spines. Color, exceedingly variable, 

 Length, 2 ■ 0. Found by Mr. Lesueur on the northern coast. 



Genus Plicatula, Lam. Animal unknown. Shell inequivalve, without ears, attenuated at the base; 



upper margin plaited, rounded ; beaks unequal, and without external facet. Hinge with two 



strong striated teeth on each valve; a pit between the two teeth for the ligament, which is 



entirely interior. 



P. ramosa. (Lam. An. sans vert. Vol. 3, p. 6.) Shell oblong-triangular, very stout and solid, with 



numerous large ramified folds. Color, white, spotted with ferruginous marks. Length, 35 - 4.0 



millimetres. 



