364 
PALAEONTOLOGY OF NEW YORK. 
GllAMMYSIA CIRCULAllIS. 
PLATE LVII, PIGS. 3-6; and PLATE LVIII, PIG. 13. 
■ Gframmysia circularis, Hat.l. Prelim. Notice Lamellibranchiata, 2, p. 51. 1S70. 
“ Pal. N. Y., vol. v, pt. 1. Plates and Explanations: PI. 57, tigs. 3-6; pi. 5S, 
fig. 13. 1833. 
Shell from medium to large size, sub-circular in outline, ventricose; length 
about one-fiftli greater than the height; basal margin regularly rounded, 
except a slight sinuosity posterior to the middle; posterior margin regularly 
rounded from the post-inferior extremity to the cardinal line. Cardinal line 
short and arcuate. Anterior end short and narrow, regularly curving from 
the lunule into the basal margin. 
Valves regularly convex along the lower portion, becoming gibbous and 
ventricose above and in the umbonal region. 
Beaks sub-anterior, prominent and strongly incurved. The beak and 
nmbo marked by a cincture, consisting of a ridge and shallow furrows, which 
becomes somewhat obsolete on the middle of the valve, but is continued to 
the basal margin, marking the shell in its passage by an undulation in the 
striae which produces a slight projection in the centre, with a shallow con¬ 
striction posterior to it. These features alternate in the two valves. 
Surface marked by fine concentric striae, which become fasciculate toward 
the base and on the anterior end, forming distinct ridges or undulations of 
the surface. No radiating striae have been observed. 
The hinge, as shown in figs. 5 and 6 of plate lvii, has a strongly marked 
ligamental area extending half the length of the shell, and a well-defined 
lunule. Figs. 3 and 4 show the anterior muscular impression just within the 
anterior border and encroaching upon the lunule. The pallial line continues 
parallel to the basal margin, recurving abruptly and terminating in the large 
posterior muscular scar on the post-cardinal slope. The course of the pallial 
line, in the cast, is marked by regular, elongate, pustulose striae, extending 
from above and terminating in that line. The interpallial area is marked by 
numerous elongate pustules. 
Three specimens measure respectively 67, 70 and 87 mm. in length, and 
