446 



NORTH AMERICAN INDEX FOSSILS. 



224. P. gastrodes Meek. (Fig. 587.) Cretacic. 



Shell thick. Surface marked with fine and closely arranged 

 growth lines. 



Benton : Kansas, Colorado. Coloradoan of Utah. 



Fig. 587. Pterin gastrodes, left valve, X 2 A- 

 (After Stanton.) 



Fig. 588. Pteria litnula, left 

 valve. (Md. Surv. ) 



225. P. nebrascana Evans and Shumard. Cretacic. 

 Differs from P. gastrodes in having smaller wings, a much 



shorter hinge line, and a much more oblique axis. Anterior ear 

 very small. Surface under a lens shows traces of small radiating 

 ribs. Average length from end of anterior ear to posterior basal 

 margin .45 inch ; length of hinge .32 inch ; convexity of the two 

 valves .15 inch. 



Montanan : Plains and Rocky Mountain region. 



226. P. limula (Conrad). (Fig. 588.) Eocenic. 

 Beak acute. Sinus of posterior ear not deep. 



Pamunky : Maryland, Virginia. 



Fig. 589. Pteronites profundus. (Pal. N. Y., V.) 



LXIX. Pteronites McCoy. 

 Differs from Actinopteria in having hinge and rest of the shell 

 much extended posteriorly. Hinge line longer than body of shell ; 



