382 
PALAEONTOLOGY OF NEW YORK. 
Valves regularly convex, becoming gibbous above the middle and in the 
nmbonal region. 
Beaks in advance of the anterior third, moderately elevated and incurved, 
rising but little above the hinge. Umbonal slope rounded, not defined. A 
broad gentle cincture extends from the beak to the ventral margin anterior 
to the middle of the length. 
Surface marked by fine, closely arranged, fasciculate concentric striae, and 
by stronger concentric folds, which are more distinctly developed in the 
anterior and umbonal region. Frequently the concentric folds are very 
irregular in their development, often bifurcating on the anterior part of the 
valves and becoming obsolete before reaching the umbonal slope. 
Ligamental area narrow. Other characters of the interior unknown. 
Three specimens have lengths of 40 mm. each and heights of 25 mm. 
Two smaller individuals measure respectively 33 and 38 mm. in length and 
19 and 22 mm. in height. 
This species bears some resemblance to G. subarcuata , but is proportionally 
more elongate and the concentric folds are much more strongly developed. 
Formations and localities. In the Waverly sandstones, at Summit and Cuya¬ 
hoga Falls, 0., and in the Lithographic limestone at Hannibal, Mo. 
Grammysia plena, n. sp. 
PLATE LXI, FIGS. 31, 32. 
In part Grmmmysia Hannibalensis (Shumard), Hall. Prelim. Notice Lamellibranchiata. 2, p. 62. 1870. 
“ “ (Leptodomus ?) Hannibalensis (Shumard), Hall. Pal. N.Y., vol. v, pt. 1. Plates and Ex¬ 
planations : PI. 61, figs. 23-88. 1883. 
Not Allorisma Hannibalensis, Shumard. Geol. Surv. Missouri, Rep., pt. ii, p. 206, pi. c, fig. 19. 1855. 
Shell below the medium size, ovate; length about one-third greater than the 
height; basal margin regularly curved from the post-basal extremity, except¬ 
ing a gentle constriction, or sinus, at about the anterior third. Posterior 
extremity obliquely truncate above. Cardinal line straight, more than half 
the length of the shell. Anterior end short, abruptly rounded below the 
lunule. Lunule deep and distinct, extending more than half way from the 
beak to the base of the shell. 
