150 
PALAEONTOLOGY OF NEW YORK. 
Ptychopteria lobata, n. sp. 
PLATE LXXXV, FIG. 37. 
Shell small, sub-rhomboidal; body broadly ovate, oblique at an angle of about 
55° with the cardinal line; length somewhat greater than the height; anterior 
margin sub-truncate; base broadly rounded; posterior margin rectangularly 
recurved into the wing. 
Left valve very gibbous; the point of greatest convexity is just below the 
umbo. Right valve unknown. 
Hinge-line straight, length nearly equal to the length of the valve. 
Beak situated anterior to the middle of the hinge, prominent, inclined 
forward, and arching over the margin of the valve. Umbonal region ample, 
gibbous, subtending an acute angle. 
Anterior end large, limited by a broad, undefined byssal depression; 
margin convex; extremity apparently obtuse. Wing small, joining the body 
at the posterior end, strongly limited by a d.eep furrow and very marked 
alar plication ; margin nearly straight; extremity angular. 
Surface marked by fine radiating striae which become finer on the wing 
and anterior end; and by striae of growth which are somewhat lamellose on 
the anterior of the shell. 
Interior unknown. 
A left valve of this species has a length of 13 mm., height 10 mm., hinge¬ 
line 11 mm. 
This species differs from P. gibbosa in its shorter, truncate anterior end, and 
stronger fold on the wing, which is comparatively stronger than in any species 
yet observed. 
Formation and locality. In the sandstones of the Upper Chemung group, 
Warren county, Pa. 
