40 PALAEONTOLOGY OF NEW YORK. 



rectiuijiular la-jik, luul more re<rularly alternating rays. Both of these forms 

 are reniarkalile for tlie very sli<:lit convexity of the left valve. 



Formation and localities. In calcareous sandstone of the Upper Cliennuig 

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



L Y l\ I () P E C T E N , Hall. 



LviaOPECTEN PARALLELODONTUS. 



PLATK IV, FR;S. 1, 2. 



LyrUrpecUn paraUclodmdiui, Hall. MS. for Pal. N. Y., VdL v. 1877. 



" " " Catalojj^ue Anier. Piiljt-dziiii' Fossils, S. A. Mili.kr. Cincinnati, 1S77. 



" '• " Pal. N. v., vol. V, lit. ]. I'lati-s and Explanations: PI. 4, tip;. 1,2. 



Jan., 1883. 



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

 the longitudinal diameter; margins regularly rounded. 



Right valve moderately convex. lA'ft valve unknown. 



Hinge-line straight; anterior poitioii not preserved in tlie spcciiiicii ; fiom 

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

 loiioitiuliiial diauictcf ol' the sliell. 



Reak obtuse, rounded, slightly ol)lique, anterior to tlie centre of the valve ; 

 uiiil)oiial region ainplc. 



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

 concave; extremity rectangular. Anterior ear not jtreserved. 



Test tliiii. iTiarked by about !)0 regular, alternating, rounded radii, with 

 concave interspaces, and crossed Ity fine, elevated, sharp, cancellating stri:\> ; 

 these are crowded over the jiosterior ear, and the I'ays are there more 

 numerous and less regnltirly alternating. 



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

 stronger rays, and shows a moderately im]iresse(l pallial line, with apparently 

 an ovate, niiiscnlar impression iicai- tlic iniiboiial region. ('artilag(>-])it suiall, 

 deeply intlented. Ligameiital area narrow, niarlved 1(\ two or tlircc slender, 

 parallel grooves, extending to the posterior extremity ; and one i>r two 



