590 CRETACEOUS PALEONTOLOGY. 



it was a part could not have been less than 30 mm. in length. 

 The surface markings of the shell resemble those of both C. 

 dumosum and C. tenuistriatu-m, but differ from both of these 

 species in having three lines of tubercles or smaller spinules 

 between the rows of larger ones instead of two only, the num- 

 ber of rows of smaller spinules upon the lateral slopes of the 

 shell being sometimes reduced to two instead of to one only 

 as in both the other species. Because of our limited knowledge 

 of this species, it is possible that some of the internal casts from 

 the Navesink marl referred to C. tenuistriatum may belong here, 

 but that can be determined only by means of more complete 

 collections. 



Formation and locality. Navesink marl, Atlantic Highlands 

 (108). 



Geographic distribution. New Jersey. 



Cardium dumosum Conrad. 

 Plate LXV., 7-10. 



1870. Cardium ( Criocardium) dumosum Con., Am. Jour. 



Conch., vol. 6, p. 75. 

 1886. Cardium (Cricocardium) dumosum Whitf., Pal. N. J., 



vol. i (Monog. U. S. G. $., vol. 9), p. 133, pi. 20, 



figs. 9 and ? 13 (not figs. 10-12). 



1905. Cardium dumosum Johns., Proc. Acad. Nat. Sci. Phil. 

 P- 15- 



Description. The dimensions of a large individual are: 

 height, 1 8 mm.; width, 18 mm.; convexity of one valve, 6 mm. 

 Shell subcircular in outline, but slightly inequilateral, moderately 

 convex. Beaks situated at about the middle of the hinge-line, 

 rather small and incurved; umbones prominent, the anterior 

 and posterior cardinal slopes about equally steep; shell slightly 

 compressed at both cardinal extremities. Surface of the shell 

 marked with about 54 rounded radiating costae, with interspaces 

 of about equal width ; from the bottom of every third interspace 

 on the central portion of the shell, there arises a row of laterally 



