40 PALEONTOLOGY OF NEW YORK. 



rectangular beak, and more regularly alternating rays. Both of these forms 

 are remarkable for the very slight convexity of the left valve. 



Formation and localities. In calcareous sandstone of the Upper Chemung 

 group, Randolph and Salamanca, Cattaraugus county, N. Y. 



LYRIOPECTEN, Hall. 



Lyriopecten parallelodontus. 



PLATE IV, FIUS. 1. a. 



Lyrurpectm parattelodontus, Hall. Ms. for Pal. N. V., vol. v. 1S77. 



" " " Catalogue Amer. Palaeozoic Fossils, S. A. Mili.uk. Cincinnati, 1^77. 



" " " Pal. N. V., vol. v. pt. 1. Plates ami Explanations: PI. 4. figs. 1,2. 



Jan., 1SS3. 



Shell of medium size, sub-orbicular, not oblique ; height somewhat less than 

 the longitudinal diameter; margins regularly rounded. 



Right valve moderately convex. Left valve unknown. 



Hinge-line straight; anterior portion not preserved in the specimen ; from 

 the beak to the extremity of the posterior ear its length is one-half the 

 longitudinal diameter of the shell. 



Beak obtuse, rounded, slightly oblique, anterior to the centre of the valve ; 

 umbonal region ample. 



Posterior car large, broad-triangular, Hat ; margin straight or slightly 

 concave; extremity rectangular. Anterior ear not preserved. 



Test thin, marked by about 90 regular, alternating, rounded radii, with 

 concave interspaces, and crossed by line, elevated, sharp, cancellating stria'; 

 these are crowded over the posterior ear, and the rays are there more 

 numerous and less regularly alternating. 



The mould of the interior preserves, around the margin, traces of the 

 stronger rays, and shows a moderately impressed pallia] line, with apparently 

 an ovate, muscular impression nearthe umbonal region. Cartilage-pit small, 

 deeply indented. Liganiental area narrow, marked by two or three slender, 

 parallel grooves, extending to the posterior extremity; and one or two 



