246 Thirty-fifth Keport on the State Mdseum. 



the stronger rays, and shows a moderately impressed pallial line, 

 with apparently an ovate, muscular impression near the umbonal 

 region. Cartilage-pit small, deeply indented. Ligamental area 

 narrow, marked by two or three slender, parallel grooves, extending 

 to the posterior extremity ; and one or two shorter accessory grooves, 

 extending for a short distance from the cartilage-pit, and parallel to 

 the longer folds. 



The specimen consists of the exterior and interior impression of a 

 right valve ; it is 38 mm. in height, 43 mm. in length, and the in- 

 • complete hinge-line measures 20 mm. from the beak to the end of 

 the posterior ear. 



This species differs from L. orbicularis in its comparatively greater 

 length, the convexity of the right valve, and the regular alternation 

 of the rays. It is remarkable as the only pectenoid form yet observed 

 in the Schoharie grit, while similar forms are numerous in the Upper 

 Helderberg limestone. 



Formation and locality. In the Schoharie grit, Albany county, 

 N. Y. 



Lyriopectest Dardantjs. 



Lyriopecten Dardanus, Hall. Pal. N. Y., vol. v, pt. 1. Plates and Explana- 

 tions : PI. 1, fig. 5. Jan., 1883. 



Shell of medium size, orbicular, transverse axis not oblique ; height 

 a little less than the length ; margin regularly rounded. Left valve 

 moderately convex. Right valve unknown. Hinge-line straight, 

 length nearly equal to the transverse diameter of the valve, extend- 

 ing as far as the posterior margin. Beak obtuse, rounded, straight, 

 anterior to the middle of the hinge-line and to the center of the 

 longitudinal diameter. Anterior ear small, narrow- triangular, flat, 

 separated from the umbo by a broad, undefined sulcus ; margin 

 slightly convex above the sinus ; extremity rectangular, rounded. 

 Posterior ear large, broad-triangular, flat ; margin straight or slightly 

 concave, rectangular to the hinge-line ; extremity mucronate. 



Test marked by about forty strong, rounded, continuous rays with 

 wider concave or flat interspaces, and sometimes a smaller inter- 

 mediate ray ; crossed by sharp, elevated concentric striae. The 

 rays are fine and little elevated on the ears, while the concentric 

 striae are conspicuous. Interior characters not observed, except an 

 indication of a well-defined ligamental area. 



The specimen is 45 mm. in height, 48 mm. in length, and the 

 hinge-line 43 mm. 



