400 CRETACEOUS PALEONTOLOGY. 



marked, the pallial line distinct. The indentation of the posterior 

 muscular ridge rather slight. 



Remarks. The specimens referred to this species are all from 

 the Hornerstown marl, and in all cases observed are associated 

 with the casts of C. vulgaris. They have very strongly the 

 aspect of immature shells, and although they are widely different 

 from the casts of the associated C. vulgaris, it is not impossible 

 that they are immature individuals of that species. In order to 

 determine the real relations of these shells, and whether C. coin- 

 pressirostra is a really valid species or not, a much larger series of 

 specimens than are now available must be studied. Whitfield's 

 type of this species is injured along the posterior margin, and in 

 his restoration he has made the shell much more quadrangular in 

 outline than it really was originally. 



Formation and locality. Hornerstown marl, J. S. Cook's pits. 

 Tinton Falls (Whitfield), near Hornerstown (152). 



Geographic distribution. New Jersey. 



Cucullaea littlei (Gabb). 

 Plate XXXIIL, Figs. 1-2. 



1876. Idonearca littlei Gabb, Proc. Acad. Nat. Sci. Phil., 1876, 



p. 316. 

 1905. Cucullaea littlei Johns., Proc. Acad. Nat. Sci. Phil., 1905, 



p. 9. 



Description. Shell very large, the dimensions of a large in- 

 ternal cast being: length 115 mm., height 89 mm., thickness 100 

 mm. Anterior margin regularly rounding from the anterior ex- 

 tremity of the hinge-line into the convex ventral margin ; postero- 

 basal margin rather bluntly rounded ; posterior margin obliquely 

 subtruncate, slightly convex; hinge line arcuate. Beaks large 

 and prominent, widely separated and much elevated above the 

 hinge-line in the cast. Valves strongly ventricose, the umbonal 

 ridge broadly rounded, the postero-dorsal slope abrupt, the pos- 

 terior surfaces of the two valves meeting at the posterior margin 

 in nearly a plane. Indentation of the posterior muscular ridge 



