576 Systematic Paleontology 



Camp Fox, Post 336, where the shells can be collected literally by the boat- 

 load. 



Pace B. Plate XXIX, Figs. 2, 3; Plate XXX. Figs. 1, 2 



(B) The second race runs larger than the first and is very much less 

 ponderous, the posterior dorsal area is usually more or less auriculate as 

 in Race A, but the two valves are much more discrepant in size, the right 

 valve being sometimes quite strongly concave. It is apparently one of the 

 races included by Weller under G. mutabilis. Although far from rare, it 

 is not so conspicuously abundant as Race A with which it is associated. 



Pace C 



(C) The third race includes thin, very strongly convex shells, agreeing 

 perfectly with Morton's figure of G. Convexa Say. It occurs at only a 

 few localities and may represent a slightly higher horizon than the 

 preceding races, although that is doubtful. 



Pace D. Plate XXXI; Plate XXXII 



(D) The fourth race quite possibly represents a distinct species; the 

 young are semi-circular in outline with a straight and very much elongated 

 hinge line ; the left valve is feebly convex, the right flattened ; the adults 

 and gerontic types are very large and ponderous and highly inflated ; they 

 attain an altitude of 120 mm., thus exceeding in size anything occurring 

 along the Canal. Two young and one adult were collected at Brightseat, 

 while a form showing the same general tendencies was found near 

 Bohemia Mills. 



Race E. Plate XXXIII, Figs. 1-3 



(E) The last race includes very thin, moderately compressed equi- 

 lateral shells from the Rancocas in the environs of Odessa, Delaware, 

 which are apparently not the G. dissimilaris Weller from the Rancocas of 

 Xew Jersey. 



Occurrence. — Race A. Matawax Formation. Opposite Post 239, 

 Camp Fox, Post 236, Post 198-199, Camp U & I, Post 192, upper and 

 lower terranes, Chesapeake and Delaware Canal, Delaware. Monmouth 



