LAMVLLUiUAXl'HIATA. II 



shorter, accessor) 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 :1S nun. in height, 43 nun. in length, and the incomplete binee- 

 line measures I'd nun. from the beak to the end of the posterior ear. 



This species differs from L. orbiculalus 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 llelderberg limestone 



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



Ltwopbcten Dabdanus. 



PLATE I. FIG. 5. 

 Lyriopecten Dardamut, Ball. Pal. N. Y., vol. v, pt. 1. Plates and Explanations : 1*1 I, 6g. 5. Jan., 1883. 



SHELL of medium size, orbicular, transverse axis not oblique; height a little less 

 than tin' length : margin regularly rounded. 



Left valve moderately convex. Right valve unknown. 



Binge-line straight, length nearly equal to the transverse diameter of the 

 valve, extending as far as the posterior margin. 



Beak obtuse, rounded, straight, anterior to the middle of the hinge-line 

 and to tin- centre 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 mucro- 



nate. 



Test marked by about forty strong rounded continuous rays with wider 

 concave or flat interspaces, and sometimes a smaller intermediate ray; crossed 

 by sharp, elevated concentric stria'. The rays are tine and little elevated on 

 the ears, while the concentric stria- are conspicuous. 

 6 



