LAMELLIBRANCHIA TA. 
365 
55, 59 and 70 mm. in height. A specimen preserving both valves has a 
length of 53 mm., height 42 mm., and a depth to both valves of 32 mm. 
This species is readily distinguished from any of its associated forms by its 
sub-circular outline, in which character it seldom varies; and also in the absence 
of a distinct cincture below the middle of the valve. 
Formations and localities. In the Hamilton group, in Albany, Schoharie and 
Madison counties; in the Chemung group, at Nichols, in Tioga county, Cort¬ 
land, Cortland county, and Ithaca, Tompkins county, N. Y. 
Grammysia elliptica. 
PLATE LV1II, FIGS. 1-12 (1,5, 6?). 
Grammysia elliptica, Hall. Prelim. Notice Lamellibranchiata, 2, p. 58. 1S70. 
“ “ “ Pal. N. Y., vol. v, pt. 1. Plates and Explanations : PI. 5S, figs. 1-12. 1888. 
Shell of medium or large size, transversely elliptical; length varying from 
one-sixth to one-third greater than the height; basal margin broadly curving, 
slightly sinuate about the middle; posterior margin abruptly rounded below 
and curving into the cardinal line above, sometimes more or less truncate. 
Cardinal line arcuate. Anterior end narrow and abruptly rounded below 
the lunule. 
Valves regularly convex below, becoming more or less gibbous above the 
middle and in the umbonal region. 
Beaks sub-anterior, very prominent, strongly incurved, rising considerably 
above the hinge-line. Umbonal slope rounded, arcuate. Cincture consist¬ 
ing of a fold and furrow, extending downward in a curving direction to 
the base of the shell, producing a gentle sinuosity in the basal margin. The 
fold is more strongly developed in the left valve and the furrow in the 
right one. 
Test thick, marked on the posterior and middle portions of the shell by 
fine, irregular, concentric striae, which become aggregated into fascicles on the 
middle of the shell; and on the anterior part marked by strong concentric 
undulations. No radiating striae have been observed. 
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