MOLLUSCA. 487 



The dimensions of the large lower valve figured by Whitfield 

 are: length, 95 mm.; width, about 55 mm. 



Remarks. This species seems to be of rather rare occurrence 

 as only fragments have been met with in the recent collections 

 of the Survey. All the specimens on record seem to have come 

 from the Navesink marl. 



Formation and locality. Navesink marl, near Crawfords 

 Corners (i26 7 ), near Walnford (i48 2 ), Cross wicks Creek 

 (195), Upper Freehold (Whitfield). 



Geographic distribution. New Jersey. 



Genus DIANCHORA Sowerby. 



Dianchora echinata (Morton). 

 Plate LI IL, Figs. 4-6. Plate LIV., Figs. 1-2. 



1835. Plagiostoma echinatum Mort, Synop. Org. Rem. Cret. 



Gr. U. S., Add. Obs., iv. 

 I 53. Spondylus capax Con., Jour. Acad. Nat. Sci. Phil, 2d 



ser., vol. 2, p. 274, pi. 24, fig. 8. 

 1864. Spondylus echinatus Meek, Check List Inv. Foss. N. A., 



Cret. and Jur., p. 7. 



1868. Spondylus echinatus Con.,' Cook's Geol. N. J., p. 724. 

 1886. Dianchora echinata Whitf., Pal. N. J., vol. I (Monog. 



U. S. G. S., vol. 9), p. 59, pi. 10, figs 3-9. 

 1905. Dianchora echinata Johns., Proc. Acad. Nat. Sci. Phil. 



(1905), p. 12. 



Description. "Shell below medium size, subcircular or very 

 broad-ovate in general outline, and with a very highly convex or 

 gibbous free valve. Lower valve fixed to foreign substances, and 

 often by nearly its entire surface, and conforming in depth to the 

 surface to which it is affixed, or nearly so. Or when more con- 

 cave the space between the margin of the shell and the object 

 to .which it is attached is filled up with shelly matter formed in 

 the same manner as the spines of the valves. The cardinal por- 

 tion of the valve is open, forming a broad triangular foramen 

 the entire width of the valve at this point, the margins of the 



