246 
PALAEONTOLOGY OF NEW YORK. 
This species is distinguished by its erect form, the broad flat interspaces 
between the radii, and the regular sharp concentric striae. 
Formation and locality. The specimen is from the higher beds of limestone 
at the Falls of the Ohio, which are of the age of the Hamilton group. 
Limoptera macroptera. 
PLATE XXIV. FIG. 11; PLATE XXVI, FIGS. 6-9; PLATE XXVII, FIGS. 1-10 ; PLATE XXVIII, FIGS. 4,5; PLATE 
XXIX, FIGS. 1-4 ; AND PLATE XGII, FIGS. 4-9. 
Lima macroptera, Conrad. Annual Report N. Y Geolog. Surv., p. 117. 1838. 
Limoptera macroptera (Conrad), Hall. Prelim. Notice Lam. Shells, etc., pt. 2, p. 17. Dec., 1869. 
“ “ “ S. A. Miller, Cat. Amer. Pal. Foss. 1877. 
“ “ “ Hall. Pal. N. Y., vol. v, pt. 1. Plates and Explanations : PI. 24, fig. 14; 
pi. 26, figs. 6-9; pi. 27, figs. 1-10 ; pi. 28, figs. 4, 5; and pl. 29, 
figs. 1-4. Jan., 1883. 
Shell large; including the cardinal expansions, the form is subquadrate; body 
broadly ovate, erect or moderately oblique; wing more or less expanded ; 
height one-fourth to one-third greater than the length; basal margin broadly 
rounded, with the anterior and posterior sides sub-parallel. 
Valves very unequal. Left valve ranging from moderately convex to 
very gibbous, often somewhat regularly arcuate from beak to base. Right 
valve smaller than the opposite, in young specimens nearly flat below, 
depressed-convex in the middle, and more convex in the umbonal region; 
in specimens of medium size there is often a greater convexity in the upper 
part, and in very old specimens the surface is depressed-convex and nearly 
flat in the lower part. 
Hinge-line straight, sometimes equalling but usually less than the length 
of the shell. 
Beak of the left valve prominent, acute, inclined forward, rising above and 
arching over the cardinal line, situated anterior to the middle of the body of 
the shell. Umbonal region prominent, convex in young shells and gibbous 
in older ones, limited anteriorly by a distinct sulcus, and posteriorly by the 
abrupt umbonal slope. Beak of right valve acute, scarcely rising above the 
liinge-line, defined anteriorly by the byssal sulcus, and posteriorly by the 
abrupt depression and distinct limitation of the wing. Umbonal angle acute. 
