6o6 CRETACEOUS PALEONTOLOGY. 



bonal region the surface is nearly smooth, being marked only 

 by more or less remote concentric lines of growth. 



Remarks. — This species differs from C. excavata in its pro- 

 portionally greater length, the average proportion of length to 

 height in the two species being i : 1.22— and i : 1.14— . On the 

 average the beaks of the Lorillard species are slightly further 

 forward, although this difference is only slight. The subtrun- 

 cate posterior margin of the Lorillard specimens is higher than 

 in C. excavata^ its middle point being at about the mid-height 

 of the shell, while in C. exccvucnta it is entirely below the mid- 

 height of the shell; the direction of this portion of the margin 

 is also' different in the twO' species, it being nearly vertical in 

 the Lorillard shells and sloping backward from below in the 

 other. The surface markings of the two species also differ, the 

 umbonal costae being coarser on the Lorillard specimens and 

 the body of the shell being smoother. 



This Lorillard species differs from C. depressa Con. (Whit- 

 field, Eigs. II and 12) in the higher position of the post-mar- 

 ginal truncation, and its different direction, it being nearly ver- 

 tical instead of sloping backward from below, and in the absence 

 of the conspicuous hump on the post-cardinal margin. The 

 species more closely resembles C. densata, but it does not grow 

 so large as that species and the posterior truncation is narrower 

 although it has the same nearly vertical position in the two 

 species. It is also' a proportionally lower and longer shell. The 

 specimen illustrated by Whitfield as C. depressa and said to have 

 been collected at Haddonfield is quite certainly not a New Jer- 

 sey specimen at all, but came from Snow Hill, North Carolina. 

 The only species which has certainly come from the Haddon- 

 field locality is like the Lorillard shell only smaller, and must 

 be called C. cretacea. 



Formation and locality. — Cliffwood clay, near Matawan 

 (107) ; Woodbury clay, Lorillard (102), near Matawan (103), 

 Crosswicks (168), near Haddonfield (183, 165) ; Wenonah sand, 

 near Marlboro (130^). 



Geographic distribution. — New Jersey. 



