654 CRETACEOUS PALEONTOLOGY. 



proportions as the type, but the two furrows originating upon 

 the anterior and posterior sides of the beak can not be detected, 

 and seem to have been absent. This may be due to the smaller 

 and possibly younger shell. 



A little shell from Corsicana, Texas, in the collection of the 

 National Museum at Washington, is apparently identical with 

 the New Jersey specimens. 



Formation and locality. Marshalltown clay-marl, near 

 Swedesboro (177); Merchantville clay-marl, Reeves' clay pit, 

 Lenola (163). 



Geographic distribution. New Jersey, Texas. 



Genus MARTESIA Leach. 



Martesia cretacea Gabb. 

 Plate LXXIV., Figs. 8-n. 



1860. Pholas cretacea Gabb, Jour. Acad. Nat. Sci. Phil, 2nd 



ser., vol. 4, p. 393, pi. 68, fig. 18. 



1 86 1. Pholas cretacea ? Gabb, Proc. Acad. Nat. Sci. Phil. 



(1861), p, 324. 

 1864. Pholas cretacea Meek, Check List Inv. Foss. N. A., Cret. 



and Jur., p. 16. 



1868. Pholas ? cretacea Con., Cook's Geol. N. J., p. 728. 

 1876. Martesia cretacea Gabb, Proc. Acad. Nat. Sci. Phil. 



(1876), p. 304. 

 1886. Martesia (Pholas} cretacea Whitf., Pal. N. J., vol. i 



(Monog. U. S. G. S., vol. 9), p. 190, pi. 25, figs. 20- 



23- 

 1905. Pholas cretacea John., Proc. Acad. Nat. Sci. Phil. 



(1905), p.. 18. 

 1905. Martesia cretacea John., Proc. Acad. Nat. Sci. Phil. 



(1905), p. 18. 



Description. Shell small, subhemispherical in front, cuneate 

 behind, the beaks strongly incurved, umbones prominent. The 

 anterior margin rounding regularly from the anterior extremity 



