6o8 CRETACEOUS PALEONTOLOGY. 



Remarks. The preceding description has been drawn up from 

 Tippah County, Mississippi specimens. In New Jersey it has only 

 been observed in the condition of poor internal casts. These 

 casts are similar in form and size, however, to the southern 

 examples, and but little doubt can be entertained as to their spe- 

 cific identity. The species resembles M. cretacea, but it is a 

 much larger shell and the hinge structure is different. 



Formation and locality. Cliffwood clay, near Matawan 

 (107); Merchantville clay-marl; near Matawan (101), near 

 Jamesburg (141), Lenola (163); Wenonah sand, near Craw- 

 fords Corner ( 1 26 3 ) . 



Geographic distribution. New Jersey, Mississippi, Texas, 

 Arkansas. 



Meretrix cretacea (Conrad). 

 Plate LXVIIL, Figs. 4-7. 



1870. Mora cretacea Con., Am. Jour. Conch., vol. 6, p. 72, pi. 



3, ng. 8. 

 1886. Mora cretacea Whitf., Pal. N. J., vol. i (Monog. U. S. 



G. S., vol. 9), p. 167, pi. 23, figs. 16-17. 

 1905. Mora cretacea Johns., Proc. Acad. Nat. Sci. Phil, 



(1905), p. 16. 



Description. Shell below medium size, the dimensions of an 

 average example are: height, 16.5 mm.; approximate length, 23 

 mm. ; convexity of one valve, 5 mm. ; somewhat triangularly 

 subelliptical in outline. Valves moderately convex, beaks small, 

 situated anterior to the middle; antero-cardinal margin con- 

 cave; anterior margin rather sharply rounded above, curving 

 more gently below and passing without interruption into the 

 broadly rounded ventral margin; posterior margin rather short, 

 obscurely subtruncate; post-cardinal margin long, gently con- 

 vex, meeting the antero-cardinal margin at the beak in an 

 angle of about 120. Postero-cardinal margin somewhat in- 

 flected, especially towards the beak; antero-cardinal margin 

 inflected in front of the beak to form a shallow lunule of 

 moderate width. Surface of shell marked by more or less 



