:,4 J>ALA:oMVLOGY of new YORK. 



The right valve is imperfect, but appears to have been iiiDrc einiilai- in 

 oiitliiH' tli;m tlu' left. 



This species is characterized by its form, smrface ornamenta,tion, and marked 

 resemblance between its right valve and the lower valves of some species of 

 the recent genus Anomia, in the tlatness of the valve and deep byssal sinus. 



Formation and locality. In the slates of the Chemung group, at Chemung 

 Narrows, Chemung county, N. Y. 



LVRIOPECTEN PrIAMUS. 



PLATE X, FIGS. 1, l. 



Lyriopecten PriatHii.'', U.KJA.. Pal. N. V.. vul. v, i>t. 1. Plates and Explanations : PI. 10, tigs. 1, 2. Jan.. 1883. 



Shell large, transversely bromlly elliptical or ovate, wider below ; transverse 

 axis niiriiial or very slightly oliliiiuc tn tlic liinge-line; height less tliaii one- 

 tenth greater than the Idiiuitmliiial diameter; margins regularly rounded. 



Left valve moderately and symmetrically convex. Right valve unknown. 



Hinge-line straight, sub-central ; length about one-half the longitudinal 

 diameter of the .shell. 



Beak obtuse, rounded, oblique, anterior lo the transver.se axis, not rising- 

 above nor extending as far as the hinge-margin. 



Anterior ear small and undefined. Posterior ear bruail-triangular, Hat; 

 margin concave ; extremity angular. Byssal sinus not defined. 



Test marked liy abnut 10 strong, rounde(|. irregular radii witli narrow 

 interspaces, crossed by fine stritB of growth. Tlie rays are often composed 

 of ftiscicles of thread-like striaj, and bifurcate at some point of their length. 

 On the posterior ear the rays are subdued and finer. 



Ligamental area 2.5 mm. wide in mature specimens, and marked by 

 numerous sharp, elevated, parallel, longitudinal stria> extending to the 

 extremities of the hinge-line. Cartilage-pit triangular, narrow, situated at 

 the apex of the beak, an<l extending to the margin of the hinge. 



One large specimen, which is a cast of the interior, measures 7:^ mm. in 

 height, 7(J mm. in length; hinge-line 32 mm. A smaller specimen, showing 



