LAMELLIBRANCHIA TA. 
51 
Posterior ear narrow-triangular, 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. 
Interior not observed. 
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 striae 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-arenaceous slates of the Chemung group 
near Cassadaga, Chautauqua county, N. Y. 
Lyriopecten magnificus. 
PLATE VIII, FIG. 8. 
Lyriopecten magnificus, Hall. Pal. N. Y., vol. v, pt. 1. Plates and Explanations: PI. 8, fig. 8. Jan., 1888. 
Shell very large, nearly circular; height a little less than the longitudinal 
diameter; basal and lateral margins regularly rounded. 
Left valve nearly flat; the greatest convexity is in the centre of the umbo- 
nal region. Right valve unknown. 
Hinge-line short, straight, length less than one-half the transverse diameter 
