584 CRETACEOUS PALEONTOLOGY. 



1886. Pachycardium burlingtonense Whitf., Pal. N. J., vol. i 



(Monog. U. S. G. S., vol. 9), p. 138, pi. 21, figs. 6-7. 

 1905. Cardium (L&vicardium) perelongatum Johns., Proc. 



Acad. Nat. Sci. Phil. (1905), p. 15. 

 1905. Cardium (Lavicardium} burlingtonense Johns., Proc. 



Acad. Nat. Sci. Phil. (1905), p. 15. 

 . 1905. Cardium (Lcevicardium) spillmani Johns., Proc. Acad. 



Nat. Sci. Phil. (1905), p. 15. 



Description. The dimensions of a nearly perfect internal cast 

 are: height, 87 mm.; width, 55 mm.; thickness, 60 mm. Shell 

 more or less narrowly subovate in lateral view, and cordate in 

 end view. Hinge-line rather short, arched, extending further 

 downward in front than behind; anterior margin convex, the 

 curvature becoming greater below; basal margin regularly 

 rounded; posterior margin longer and straighter than the an- 

 terior, usually slightly convex, sometimes straight or slightly 

 sinuate in the casts a little above the middle. Beaks situated 

 back of the middle of the hinge-line, strongly elevated above it 

 in the casts, pointed, incurved, and distinctly curved forward. 

 Umbones prominent, the most prominent portion of the shell 

 being in an oblique line from the beaks to the postero-basal 

 margin, this umbonal prominence being not at all angular. The 

 posterior slope much more abrupt than the anterior, its surface 

 conspicuously impressed above the middle of the shell about half 

 way between the top of the umbonal prominence and the pos- 

 terior cardinal extremity. Muscular impressions large, the an- 

 terior ones deeply impressed, the posterior ones scarcely or not 

 at all differentiated from the surface of the casts. The left valve 

 with two strong cardinal teeth beneath the beak with a pit be- 

 tween, right valve with a single cardinal tooth; anterior lateral 

 teeth more remote from the cardinal teeth than the posterior 

 ones, and also apparently much stronger. Inner free margin 

 of the valves crenate along the posterior margin, smooth along 

 the basal and anterior margins. Surface of the shell marked 

 by radiating ribs upon the posterior slope, 'which, in the internal 

 casts at least, continue only from the margin up to the umbonal 



