LAMELLIBRANCHIA TA. 
237 
PTERONITES, McCoy. 
Pteronites profundus. 
PLATE XXII, PIGS. 25, 26, 27. 
Pteronites profundus, Hall. Pal. N. Y., vol. v, pt. 1. Plates and Explanations: PL 22, figs. 25-27. 
Jan., 1883. 
Shell large, longitudinally semi-ovate; body semi-elliptical, arcuate, oblique 
to the hinge-line at an angle of about 30°; length about twice the height; 
anterior margin very oblique, slightly concave beneath the beak and gradu¬ 
ally curving into the broadly rounded basal margin; posterior margin 
obliquely truncate, slightly curving below. 
Left valve convex in the lower part, gibbous from the middle upwards. 
Right valve unknown. 
Hinge-line straight; length more than the greatest length of the shell. 
Beak sub-anterior, obtuse, rising but little above the hinge-line, and 
apparently not incurved. Umbonal region very gibbous, subtending an acute 
angle. 
Anterior end produced, into an acute extension which is limited by a very 
shallow byssal depression. Wing not defined, extending from the beak the 
entire length of the shell, and produced beyond the posterior extremity of 
the body; margin very slightly concave, extending at nearly right angles to 
the axis of the body. 
Test of moderate thickness, marked by concentric striae. The casts show 
distant, irregular, concentric undulations. 
Hinge with a single continuous groove. The pallial line extends parallel 
to the ventral margin, from a point anterior to the beak to below the middle 
of the length of the body. 
A large left valve has a length of 78 mm., with a height of 38 mm., and 
hinge-line 90 mm. A smaller example has a length of 37 mm., height 
23 mm., and hinge-line 40 mm. 
