Lamellibrastchiata. 257 



specimen, showing the exterior, is 63 mm. in height, 57 mm. in 

 'longitudinal diameter, and hinge-line about 31 mm. 



In general appearance of surface this shell is similar to L. macro- 

 dontus, but the details are quite different. This species, though 

 characterized from the left valve only, is distinctly different from the 

 others in form and surface ornamentation. 



Formation and locality. Associated with numerous segments of 

 crinoidal columns and rarely with any other fossils, in the upper part 

 of the Chemung group at Franklin, Delaware county, N. Y. 



Lyriopecten" fasciatus. 



Pernopecten fasciculatus, Hall. MS., vol. v, pt. 1. 1877. 



Miller, Cat. Amer. Pal. Foss. p. 200. 1877. 

 Not Auculopecten fasciculatus, Hall. 



Lyriopecten fasciatus, H all. Pal. N. Y.,vol. v, pt, 1. Plates and Explanations: 

 PI. 9, figs. 10, 11. Jan., 1883. 



Shell of medium size, very broadly ovate, erect ; length a little less 

 than the width ; margins regularly rounded. Eight valve convex, 

 the greatest convexity one-third the width of the valve from the 

 beak. Left valve unknown. Hinge-line short, straight. Beak 

 acute, erect, prominent; umbonal region distinctly defined, sub- 

 tending a right angle. Anterior ear small, scarcely defined, about 

 half the length of the posterior one. Posterior ear triangular, de- 

 fined by a well-marked sulcus; margin nearly straight; extremity 

 obtuse. Byssal sinus shallow. 



Surface ornamented by strong, low, broad, rounded radii, which 

 increase by interstitial addition ; and numerous sharp, elevated, 

 radiating striae mark the surface of the rays, giving them a dis- 

 tinctly fasciculated aspect. These also mark the interspaces, which 

 are narrower than thej large rays. Sharp, regular, concentric striae 

 cancellate the radii. The ears are marked only by the concentric 

 striae, which are less prominent than on the body of the valve. 



The specimen described is a right valve, having a length of 34 

 mm., height 36 mm., and hinge-line about 10 mm. 



In outline and surface characters this species resembles L. Priamus, 

 but the valve is more convex than the specimen referred to the right 

 valve of that species ; it is also less oblique, and the beak more ele- 

 vated and erect. The rays of L. Priamus are distinctly and fre- 

 quently bifurcating, while in this species the fasciculate appearance is 

 due to the sharp, elevated striae upon the stronger rays. 



Formation and locality. Chemung group, Leon, Cattaraugus 

 county, N. Y. 



[Sen. Doc. No. 38.] 33 



