MOLLUSCA. 651 



< 



Super-family ADESMACEA. 

 Family PHOLADIDAE. 



Genus PHOLAS Linneus. 

 Pholas cithara Morton. 

 Plate LXXIV., Fig. 7. 



1834. Pholas cithara Morton, Synop. Org. Rem. Cret. Gr. U. 



S., p. 68, pi. 9, fig. 10. 

 1852. Pholas pectrosa Con., Proc. Acad. Nat. Sci. Phil. (1852- 



53), p. 200. 

 1854. Pholas pectrosa Con., Jour. Acad. Nat. Sci. Phil., 2nd 



sen, vol. 2, p. 299, pi. 27, fig. 9. 

 1861. Pholas cithara Gabb, Synop. Moll. Cret. Form., p. 222 



(166). 

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



and Jur., p. 16. 



1868. Clavipholas cithara Con., Cook's Geol. N. J., p. 728. 

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



(1876), p. 304. 

 1886. Pholas cithara Whitf., Pal. N. J., vol. i (Monog. U. S. 



G. S., vol. 9), p. 187, pi. 25, figs. 14-16. 

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



(1905), p. 18. 



Description. Shell subovate in outline, sometimes more or 

 less pointed posteriorly and subtruncate anteriorly, giving to it 

 a subtriangular outline. Hinge-line straight, one-half or more 

 than one-half the length of the shell; anterior margin rounded, 

 basal margin gently convex, straight or sometimes slightly sin- 

 uate; postero-ventral extremity more or less sharply rounded, 

 postero-dorsal margin oblique, gently convex to the posterior 

 extremity of the hinge-line. Beaks situated about one-sixth of 

 the length of the shell from the anterior extremity, rather broad, 

 enrolled and approximate. Valves most prominent along a line 

 extending almost vertically from the anterior side of the beak to 

 the ventral margin of the shell; from this rounded umbonal 

 prominence the surface slopes abruptly to the anterior margin 



