MARYLAND GEOLOGICAL SURVEY 673 



Outside Distribution. Matawan Formation.. Merchantville clay marl, 

 Marshalltown clay marl, Wenonah sand, New Jersey. Monmouth Forma- 

 tion. Navesink marl, New Jersey. 



CARDIUM KUMMELI Weller 



Cardium kummeli Weller, 1907, Geol. Survey of New Jersey, Pal., vol. iv, 

 p. 585, pi. Ixvi, figs. 1-3. 



Description. " The dimensions of a rather small internal cast of a 

 right valve are : Height 45 mm., width 34 mm., convexity 17.5 mm. 

 Large individuals sometimes attain a height of 70 mm. or more. Shell 

 subovate in lateral view, cordate in end view. Beaks of the internal casts 

 greatly elevated above the hinge line, pointed and incurved. Hinge line 

 arcuate; anterior margin regularly rounded from the extremity of the 

 hinge line to the middle of the basal margin ; postero-basal margin a little 

 more sharply rounded; posterior margin convex, a little straighter than 

 the anterior. Valves strongly convex or gibbous, most prominent, but 

 not at all angular, along an oblique line from the beaks to the postero- 

 basal extremity, the posterior slope more abrupt than the anterior. Mus- 

 cular impressions large, the anterior ones deeply impressed above, the pos- 

 terior one scarcely differentiated from the general surface of the casts. 

 Hinge characters not seen. Inner free margins of the valves apparently 

 not crenate. Shell substance thick, rugose externally. The surface mark- 

 ings consist of strongly elevated, rounded, radiating costae, narrower than 

 the interspaces; on a specimen about 55 mm. in length the distance 

 between these ribs from center to center at the middle portion of the shell 

 margin is about 2 mm. or a little less. Each third interspace is occupied 

 by a row of strong and thick spines rising 1 or 2 mm. above the tops of the 

 costee when complete, subcircular in cross-section, their bases occupying 

 the entire width of the furrow, the space between successive spines being 

 about equal to the thickness of the spines themselves ; in some cases the 

 bases of the spines are thickened longitudinally so that they occupy essen- 

 tially the entire furrow, in which case the two bounding costse with the 

 row of spines rising from the intervening furrow appear to form alto- 

 gether one broad rib supporting a row of strong spines. The two furrows 



