322 Thirty-fifth Report on - the State Museum. 



extremity, limited by a furrow which is not conspicuous in the 

 lower part, but in the right valve is more marked; margin obliquely 

 truncate. 



Surface marked by fine radii, which are distinctly cancellated by 

 the concentric striae, when the specimen is tolerably well-preserved; 

 also by concentric lines of growth which, at somewhat regular in- 

 tervals, are sharply elevated. The radii are obsolete on the anterior 

 of the valve, and the concentric striae are lamellose. The connected 

 valves show a narrow ligamental area extending half the length of 

 the hinge. Other characters of the interior are unknown. 



One specimen has a length of 35 mm., height 21 mm., and hinge- 

 line 25 mm. Another has a length of 25 mm., height 13 mm., 

 and hinge-line 20 mm. 



This species resembles P. Eucrate, but is less gibbous, more elon- 

 gate, and without angularity along the body. 



Formation and locality. In a conglomerate of the Chemung group 

 at Panama, Chautauqua county, N. Y. 



PtYCHOPTERIA GrALEKE. 

 Ptychopteria Galene, Hall. Pal. N. Y., vol. v, pt. 1. Unpublished. 



Shell small, rhomboidal; body sub-elliptical, oblique at an angle of 

 about 40° with the hinge; height greater than half the length ; 

 ante-byssal margin oblique, curving gently into a shallow sinus; 

 base regularly rounded; posterior end abruptly recurved. Left 

 valve convex, moderately gibbous on the umbo, and sub-angular 

 along the upper half. Right valve less convex above, depressed- 

 convex in the lower part. Hinge-line straight, length greater than 

 the height of the valve. Beaks near the anterior third of the 

 hinge, inclined forward, prominent, arching over the hinge-line. 

 Umbo gibbous, subtending somewhat less than a right angle. Ante- 

 rior end small, limited by the shallow, nearly vertical byssal depres- 

 sion; extremity acute. "Wing wide-triangular, joining the body 

 near the posterior end; limiting furrow distinct; fold wide and 

 moderately prominent; margin obliquely truncate, very slightly 

 concave just below the hinge-line ; extremity angular. 



Surface of the body and wing marked by regular, fine, interrupted 

 or undulating radii, which are obscure or obsolete on the anterior 

 portion ; also by very fine concentric lines, which are crowded into 

 irregular fascicles and are lamellose " on the anterior part of the 

 valve. 



