LAMELLIBRAN CHI A TA. 
383 
Valves regularly convex in the posterior portion, becoming very gibbous 
and ventricose in the middle and umbonal region. 
Beaks sub-anterior, prominent and strongly incurved. Umbonal slope 
sub-angular, extending to the post-inferior extremity, producing a slight 
angularity in the margin. Post-cardinal slope broad, marked lay a distinct 
fold along the middle, which produces an undulation in the margin of the 
shell. A shallow cincture extends from the beak, reaching the ventral 
margin at about the anterior third. 
Surface marked by fine concentric striae, which are somewhat fasciculate 
on the posterior portion of the shell, and by fine radiating pustulose striae in 
well-preserved specimens. The anterior half of the shell is marked by 
strong sub-angular folds, or undulations, which become obsolete on the mid¬ 
dle of the shell, or sometimes extending to the umbonal angle. These con¬ 
centric folds are frequently bifurcate at or about the cincture. Interior 
essentially unknown. 
Two specimens measure respectively 36 and 39 mm. in length, and 22 and 
22 mm. in height. 
This species more nearly resembles G. Hannibalensis than any other, but the 
shell is more gibbous, the cincture is stronger, the posterior extremity very dis¬ 
tinctly truncate and the post-cardinal slope with a more or less defined fold. 
Formation and locality. In the yellow sandstones at Burlington, Iowa. 
Grammysia (Sphenomya) cuneata. 
PLATE LXII, FIGS. 1-9 ; AND PLATE XCIII, FIG. 19. 
Grrammysia ( Sphenomya ) cuneata, Hall. Pal. N. Y., vol. v, pt. 1. Plates and Explanations: PI. 62, fig-s. 
1-9. 1883. 
Shell of small or medium size; ovate-cuneate, very oblique ; length more than 
one-half greater than the height; basal margin regularly curved, with some¬ 
times a visible constriction toward the posterior end. Posterior end nar¬ 
rowly rounded at the extremity and obliquely truncate above. Cardinal 
line short; margins apparently not inflected. Escutcheon large, limited by 
an indistinct groove and fold. Anterior end very short, abruptly rounded 
below the lunule. 
