241 



Fig. 153. Aviculopecten princeps. A large left valve, much extended posteriorly 

 (from Hall J. 



Found in the Enerinal limestone, at Section 5 (rare) ; in 

 the shale down to and in the Trilobite beds, at Sections 6, 7, 

 8, and on the Lake Shore (rare) ; also in the shale below the 

 Trilobite beds, in Avery's Creek. 



Aviculopecten exacutus. Hall. (Fig. 153.) (Pal.N.Y., 

 Vol. V., Pt. I., p. 8, PI. III.) 



Distinguishing Characters. — Beak more acute than in the 

 preceding species ; proportionally larger wing; concave pos- 

 terior margin; sharp alternating rays, with broad concave 

 interspaces, extending into the ear and wing. 



Fig. 153. Aviculopecten exacutus. Right and left valves, from Hamburg. Erie Co., 

 N. Y.; the figure of the left valve does not show the concentric lamellae, and the beak is 

 represented as too acute (from Hall). 



