420 



NORTH AMERICAN INDEX FOSSILS. 



Fig 



Clinton and Niagara : New York, New Jersey (Decker Ferry), 

 New Hampshire ? 



1 54. P. striaecosta McChesney. (P. brisa Hall.) Siluric. 



Surface marked with strong, radiat- 

 ing and concentric striae and broad 

 radiating ribs. 



Clinton: Ohio, Indiana, Kentucky. 

 Niagaran : Indiana, Wisconsin. 



155. P. lanii Grabau. (Fig. 547.) 



Siluric. 

 Strongly oblique, surface with con- 

 centric striae only. 

 Lower Monroe (Raisin River) of Michigan, Ohio and Canada. 



156. P. securiformis (Hall). (Fig. 548.) 



Upper Siluric-Lower Devonic. 



Shell convex. Anterior ear practically ab- 

 sent ; posterior small. Surface covered with 

 concentric striae and distant strong radiating 

 ones. 



Cobleskill : New York. Helderbergian : 

 New York, Oklahoma. 



157. P. naviformis (Conrad). (Fig. 549.) 



546. Pierinea emacerata. 

 (Pal. N. Y., II.) 



Fig. 547. Pierinea 

 lanii, left valve of a 

 small individual. (Af- 

 ter Whitfield. \ 



\ 



Devonic. 



Similar to Actinopteria com- 



— -fn munis but differs in its much 



larger posterior ear and in its 



1 1 obscure radiating and concen- 



f ^ trie striae. 



Helderbergian : New York, 

 ■■ \ -\ Gaspe. 



H 158. P. gebhardi (Conrad). 

 (Fig. 550.) Devonic. 



I H H Large, suborbicular. Left 



■ v 



valve marked with about 1 5 

 slightly impressed radiating 

 (Pal. N. grooves, forming faint, wide 

 and convex ribs. Ears equal, 

 not produced. Height about 5 inches. 

 Oriskany : New York. 



Fig. 548. 



Pierinea securiformis. 

 Y., III.) 



