590 CRETACEOUS PAI.EONTOLOGY. 



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

 The surface markings of the shell resemble those o>f both C. 

 dumosum and C. temdstriaiiim, but differ from both of these 

 species in having three lines of tubercles 01 smaller spinules 

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

 ber O'f 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 

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

 the Navesink marl referred tO' C. tenmstriatum may belong here, 

 but that can be determined only by means of more complete 

 collections. 



Pormastion and locality. — Navesink marl, Atlantic Highlands 

 (108). 



Geographic distribution.— "New Jersey. 



Cardium dumosum Conrad. 



Plate LXV., 7-10. 



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



Conch., vol. 6, p. 75. 

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



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



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

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



(1905), P- 15- 



Description. — The dimensions of a large individual are: 

 height, 18 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 costse, 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 



