494 



NORTH AMERICAN INDEX FOSSILS. 



Chemung Group : New York, Pennsylvania. 

 361. P. suborbicularis Hall. (Fig. 661, b.) Devonic. 



Depressed-convex. Extremities of ear angular. Rays regu- 

 lar, about equalling the interspaces, crossed by concentric lamel- 

 lae. Differs from Lyriopecten orbiculatus in lacking broad ligament 

 area. 



Chemung Group : New York, Pennsylvania. 



XCV. Lyriopecten Hall. 

 Differs from Aviculopecten in the much less distinct ears and in 



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Fig. 662. Lyriopecten orbiculatus. a, ligament area of right valve, X 3 > ?>> interior 

 of left valve; c, d, L. tricostatus, left valve and enlargement of surface. (Pal. N. Y., V.) 



the rounded anterior ear, which is much smaller than the posterior 

 ear or absent. Devonic. 



362. L. orbiculatus Hall. (Fig. 662, a, b.) Devonic. 



Length and height about equal. Beak obtuse. Surface 



