LAMELLIBRANCHIA TA. 
55 
the exterior, is 63 mm. in height, 57 mm. in longitudinal diameter, and 
hinge-line about 31 mm. 
In general appearance of surface this shell is similar to L. macrodontus , but 
the details are quite different. 
This species, though characterized from the left valve only, is distinctly 
different from the others in form and surface ornamentation. 
Formation and locality. Associated with numerous segments of crinoidal 
columns, and rarely with any other fossils, in the upper part of the Chemung 
group, at Franklin, Delaware county, N. Y. 
Lyriopecten fasciatus. 
PLATE IX, FIGS. 10, 11. 
Pernopecten fasciculatus, Hall. MS., vol. v, pt. 1. 1877. 
“ “ “ Catalogue Amer. Palaeozoic Fossils, Miller, p. 200. 1877. 
Not Aviculopecten fasciculatus, Hall. 
Lyriopecten fasciatus. Hall. Pal. N. Y., vol. v, pt. 1. Plates and Explanations : PL 9, figs. 10, 11. 
Jan., 1883. 
Shell of medium size, very broadly ovate, erect; length a little less than the 
width ; margins regularly rounded. 
Right valve convex, the greatest convexity one-third the width of the 
valve from the beak. Left valve unknown. 
Hinge-line short, straight. 
Beak acute, erect, prominent; umbonal region distinctly defined, sub¬ 
tending a right angle. 
Anterior ear small, scarcely defined, about half the length of the posterior 
one. Posterior ear triangular, defined by a well-marked sulcus; margin 
nearly straight; extremity obtuse. Byssal sinus shallow. 
Surface ornamented by strong, low, broad, rounded radii, which increase 
by interstitial addition; and numerous sharp, elevated, radiating striae mark 
the surfaces of the rays, giving them a distinctly fasciculated aspect. These 
also mark the interspaces, which are narrower than the large rays. Sharp, 
regular, concentric striae cancellate the radii. The ears are marked only by 
the concentric striae, which are less prominent than on the body of the valve. 
