FAMILY CARDIDJE CARDIUM. 207 



Cardium MORTONI. 



PLATE XXIII. FIK 251. 



(STATE COLLECTION.) 



Cardium mortoni. Conrad, Jour. Acad Nat. Sc. Vol.6, p. 259, pi. 11, figs. 5, 6, 7. 

 C. id. Gould, Invertebrata of Mass. p. 91. 



Description. Shell small, thin, inflated, globular, slightly oblique. Surface smooth and 

 destitute of ribs or rays : posterior side somewhat obliquely extended ; margin entire, or ob- 

 soletely serrated ; beaks large, tumid, subcentral, contiguous. 



Color. Epidermis scanty, dingy-white ; beneath which it is yellowish, the beaks yellow : 

 an oblong dark purple spot on the posterior side. Interior with faint radiating striae : the 

 cavity bright sulphur yellow ; margins white. 



Length and breadth, 0*5 - - 9. Diameter, 0*3 - 0-6. 



This is a very common shell along the shores of Long island sound. It is closely allied to 

 the C. IcRvigatum of the Antilles; according to Dr. Gould, but wants the purple blotch on th 

 posterior margin, and is more smooth and polished on its surface. 



{EXTRA-LIMITAL.) 



C. fasciatum. (Montagu, Suppl. 30, pi. 27, fig. 6.) Shell ovate-rotund, pellucid. Valves with 

 about 27 longitudinal ribs, and a few distant elevated striae, which, are often obsolete towards the 

 hinge. Color, whitish, with transverse interrupted brown bands, which appear, especially within, 

 like series of oblong spots. Length, • 25 ; width, • 4. Common to both Continents. 



C. muricatum. (Lin. p. 1123. Lam. Vol. 3, p. 626.) Shell ovate, heart-shaped. Valves with 36 

 ribs, of which 12 have their spines directed in an opposite direction to the others; marginal ser- 

 ratures largest on the anterior edge. Color, greyish or yellowish white, edged with orange-yellow 

 or scarlet on the anterior side, and sometimes stained with red. Length, 1*5; width, 1 -4 ; diame- 

 ter, 1 '0. South Carolina, Florida. 



C. ventricosum, Brug. (Lam. Vol. 3, p. 627.) Shell ventricose, almost heart-shaped. 33 - 34 ribs, 

 of which seven at the anterior end are flattened and somewhat imbricated, and a few at the posterior 

 end are without the scaly striae which cross the others ; one edge of the middle ribs is more rounded 

 than the other, and they all form crenatures on the margin of the shell. Color, rusty spotted, and 

 irregularly banded transversely with biown. Length, 2 *2 -4 -5: width, 2*0 - 4*0; diameter, 

 1 '7 - 3 -5. South Carolina. 



