450 CRETACEOUS PALEONTOLOGY. 



mens more or less closely resemble Gryphaea convexa, in minia- 

 ture, even to the oblique posterior constriction and the consequent 

 auriculation of the shell, and Whitfield has referred the species 

 to the genus Gryphaea instead of Ostrea. The convex valve, 

 however, in most cases gives evidence of having been attached, 

 and the beak is usually not strongly incurved, characters which 

 would seem to ally the species to the genus Ostrea rather than 

 GrypJmea. Those types of Whitfield's O. glandiformis which 

 preserve the shell are a perfectly normal upper valve of O. 

 bryani and one of the more shallow lower valves of the same 

 species. The most common occurrence of the species is in the 

 form of internal casts such as is illustrated by Whitfield under 

 the name O. glandiformis. Only at the marl pits near Vincen- 

 town have the shells themselves been found abundantly. 



Formation and locality. Vincentown limesand, near New 

 Egypt (Whitfield); Manasquan marl, near Vincentown (159), 

 near Farmingdale (138), near New Egypt (155). 



Geographic distribution. New Jersey. 



Genus GRYPHAEA Lamark. 



All the specimens of Gryphaea in the Cretaceous beds of New 

 Jersey have usually been referred to a single species, G. vesicu- 

 laris Lam. In the present report this usage has been departed 

 from and three distinct forms have been recognized. These 

 forms are distinct varieties, at least, are easily recognized, 

 are characteristic of distinct horizons, and are connected by very 

 few or no intermediate forms. There may be differences of 

 opinion as to the advisability of recognizing them as of specific 

 rank, but it really makes little difference whether they be con- 

 sidered as varieties or as species. It is certainly more convenient 

 to designate a given form by a single name rather than by two, 

 and so the names are considered to be of specific rank in this con- 

 nection. 



