LAMELLIBRANCHIA TA. 
421 
Valves moderately convex below, gibbous in the middle and above. 
Beaks prominent, attenuate. 
Surface marked by fine, undulating concentric striae and by about forty- 
five rounded radii, with narrow interspaces. Some of the radii become less 
conspicuous and duplicate upon the posterior slope. 
The specimen described has a length, in its compressed condition, of about 
28 mm. and a height of 31 mm. 
In form this species is similar to P. retusa , but the shell is less oblique, the 
posterior slope longer and the radii are more direct. 
Formation and locality. In the Marcellus shale; precise locality unknown. 
# 
Panenka retusa, n. sp. 
PLATE LXIX, FIG. 6. 
In part Cardiula? radians (Conrad), Hall. Pal. N. vol. v, pt. 1. Plates and Explanations: PL 69, 
figs. 5-11. 1883. 
Shell of medium size, obovate, oblique; length nearly equal to the height, 
Pallial margin regularly curving. 
Valves moderately convex below and in the middle, becoming gibbous in 
the umbonal region. 
Hinge-line short, straight. Ligamental area distinct. 
Beaks sub-central, small, curving forward, not prominent. 
Surface concentrically striated, and marked by about thirty-five moderately 
rounded, curving plications, with somewhat narrower interspaces. 
The specimen described has a length of 30 mm. and a height of 31 mm. 
This species is distinguished by its broad obovate form, its sub-equal length 
and height, and by its regular curving simple plications. 
Formation and locality. In the shales of the Hamilton group on the shore of 
Cayuga lake, N. Y. 
54 
