254 Thirty-fifth Keport on the State Museum. 



one- third longer than the anterior, the limits not well-defined, and 

 it appears as an expansion or extension of the posterior side of the 

 umbo ; margin concave ; extremity mucronate. Anterior ear short- 

 triangular ; margin convex ; extremity rounded, separated from the 

 umbo by a deep, rounded sulcus, which corresponds to the byssal 

 sinus. 



Test ornamented by about 25 irregular, strong, rounded rays, with 

 wider interspaces, marked by two or three smaller lines in each one, 

 and crossed by fine striae of growth. The surface markings extend 

 over the ears. 



The valve described is 28 mm. high, and of about the same 

 length, and the hinge-line 18 mm. The length of the posterior ear 

 is 11 mm., and of the anterior ear 7 mm. 



This species bears some resemblance to L. solox, but differs in the 

 flatness of the valve and less gibbous umbo. In surface character it 

 is similar to L. tricostatus, but has fewer intermediate strise between 

 the stronger rays, which in that species are more simple and rounded ; 

 while in other characteristics they are very unlike. 



Formation and locality. In argillo-arenacous slates of the Che- 

 mung group near Cassadaga, Chautauqua county, N. Y 



Lyriopecten- magntficus. 



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

 tions: PL 8, fig. 8. Jan., 1883. 



Shell very large, nearly circular ; height a little less than the longi- 

 tudinal diameter; basal and lateral margins regularly rounded. 

 Left valve nearly flat ; the greatest convexity is in the center of the 

 umbonal region. Right valve unknown. Hinge-line short, straight, 

 length less than one-half the transverse diameter of the valve, ex- 

 tending farther toward the posterior than toward the anterior 

 margin. Beak obtuse, rounded, central to the body of the shell, 

 depressed, not rising above the hinge-line, nor extending to the 

 hinge-margin; umbonal region moderately convex, not defined 

 laterally. Anterior ear small, narrow-triangular, not well-defined; 

 extremity very obtuse, rounded ; margin slightly concave without a 

 decided byssal sinus. Posterior ear triangular, more than twice the 

 length of the anterior and defined from the umbonal slope by the 

 absence of the strong radii; extremity acute-angular; margin 

 marked by a broad, rounded sinus. 



Test marked by about 40 strong, elevated rays, which are some- 

 what flattened along their summits; usually alternating with one or 



