LAMELLIBRANCHIA TA. 
381 
Valves regularly convex toward the ventral margin, depressed-convex at 
the posterior end and ventricose in the middle and above. 
Beaks at about the anterior third, large and prominent, incurving over 
the hinge-line. Umbonal slope convex, gibbous above and gradually de¬ 
clining into the general surface of the shell. Cardinal slope marked by one 
or two inconspicuous folds. Cincture vertical, not strongly defined. 
Surface marked by fine concentric striae and by numerous concentric folds, 
which are strong and angular upon the anterior end, becoming regularly 
bifurcated along the line of the cincture and thence continued to the 
post-cardinal slope where they become rather abruptly obsolete. Interior 
unknown. 
The specimen described has a length of 28 mm. and a height of 17 mm. 
This species is distinguished by the regular duplication of the concentric folds 
along the cincture. It is more gibbous than either G. communis or G. ffan- 
nibalensis, more abruptly depressed at the posterior extremity, and distinctly 
angular at the anterior end, a feature observed only in the first species here 
cited. 
Formation and locality. In the upper beds of the Chemung group, at Warren, 
Pa. 
Grammysia Hannibalensis. 
PLATE LXI, FIGS. 29, 30, 33. 
Allorisma Hannibalensis, Shumakd. Geol. Surv. Missouri, Rep., pt. ii, p. 206, pi. c, fig-. 19. 1855. 
In part Grammysia Hannibalensis (Shumard), Hall. Prelim. Notice Lamellibranchiata, 2, p. 62. 1870. 
“ “ ? “ “ Meek. Pal. Ohio, vol. ii, p. 300. PI. 16; figs, 5a, b, c. 1875. 
“ “ ( Leptodomusl?) Hannibalensis (Shumard), Hall. Pal. N. Y., vol. v, pt. 1. Plates and Ex¬ 
planations : PI. 61, figs. 23-83. 1883. 
Shell below medium size, narrowly ovate or sub-elliptical; length more than 
one-third greater than the height; basal margin gently curved, more abruptly 
curving at the anterior end, with a gentle sinus anterior to the middle. 
Posterior extremity regularly rounded to about the middle of its height and 
sub-truncate above. Cardinal line straight, extending more than half the 
length of the shell. Anterior end abruptly rounded below the lunule. 
49 
