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PALEONTOLOGY OF NEW YORK. 
Pterinea consimilis. 
PRATE XVI, PIGS. 1, 2, 8, 9,. 11 ; AND PLATE LXXXIV, FIG. 23. 
Pbei'inea consimilis, Hall. Pal. N. Y., vol. v, pt. 1. Plates and Explanations: PI. 15, figs. 1, 2, 8, 9, 11. 
Jan., 1888. 
Shell large, sub-rhomboidal, nearly orbicular; length greater than the height; 
margins regularly curved, moderately produced on the posterior end. 
Left valve convex above, depressed-convex below. Right valve convex on 
the umbo, flat or slightly concave below. 
Hinge-line straight, length equal to or a little greater than the length of 
the valve. 
Beak acute, anterior, inclined slightly forward, not rising above the hinge. 
Umbonal region prominent but not strongly limited, subtending more than a 
right angle. 
Ear small, limited by the abrupt slope of the umbo, which becomes a dis¬ 
tinct sulcus in the right valve; margin convex (except in the byssal sinus); 
extremity rounded. Byssal sinus not distinct. Wing broad, triangular, 
undefined, much extended; margin concave; extremity acute. 
Surface of left valve marked by numerous flattened, slender, filiform rays, 
with broad, flat interspaces, which are marked by one or two, more or less dis¬ 
tinct, finer rays. The radii are often undulating, and become obscure towards 
the base. The cardinal expansions are correspondingly marked. Fine, closely 
arranged, inconspicuous concentric striae cross the surface. The wings of 
both valves are similar in surface characters. The body of the right valve 
shows the concentric striae, with obscure indications of rays. 
Ligamental area broad, marked by fine parallel grooves the entire length. 
Lateral teeth two, strong, converging. Cardinal teeth preserved as three short 
plications under the beak of the left valve. Pallial line simple, originating 
anterior to the beak, continuing nearly parallel to the margin of the valve, 
recurving and terminating in a large muscular scar on the post-cardinal slope 
adjacent to the wing. 
A left valve has a length of 52 mm., height 49 mm., hinge-line about 50 
