248 



NORTH AMERICAN INDEX FOSSILS. 



160. P. punctatus (Martin). (Fig. 298, d-e.) 



Upper Carbonic. 



Distinguished by its large size, hinge line shorter than the width 

 of the shell below, slight mesial sinus in the pedicle valve, small, 

 incurved beak and numerous regular concentric folds with plain 

 interspaces. Spines numerous, minute and appressed. 



Widely distributed throughout North America. 



Fig. 2c 



a-c, Productus nebraskaensis ; d, e, P. punctatus (Ind. Geol. Surv. ) 



161. P. symmetricus McChesney. (Fig. 299.) 



Upper Carbonic. 

 Cardinal area a little less than greatest width of shell. Front 

 broadly rounded. Pedicle valve without mesial sinus ; ears ob- 

 tusely angular, not well defined from the body of the shell. 

 Brachial valve moderately concave. Surface covered with small 

 concentric wrinkles, covered with many minute spines. Width 



