472 



NORTH AMERICAN INDEX FOSSILS. 



shell by a conspicuous sinus, extending from the beak obliquely 

 backward. Upper valve flat. 



Forms a conspicuous bed in the middle of the Navesink of 



Fig. 629. Gryphcea convex a, X 



New Jersey ; also in Marshalltown of New Jersey. Also in 

 Ripleyan of Alabama and Mississippi. 



294. G. newberryi Stanton. (Fig. 630.) Cretacic. 



Outline rounded. Beaks broad. Surface marked with con- 



FlG. 630. Gryphcea newberryi. (After Stanton. ) 



centric lines which occasionally become somewhat lamellose. 

 Coloradoan : Colorado, Utah, New Mexico, Arizona, Texas. 



LXXXI. Exogyra Say. 

 Shell massive. Left or under valve always much the deeper. 

 Right or upper valve usually flat. Shell fixed by the left valve. 

 Beak of lower valve always turned strongly backwards and usually 

 more or less spiral. Beak of upper valve inconspicuous but de- 

 flected or spiral. Upper Jurassic-Cretacic. 



