138 
PALEONTOLOGY OF NEW YORK. 
Ptychoptekia Eudora, n. sp. 
PLATE LXXXV, FIG. 9. 
Shell of medium size, rhomboidal; body narrow, elongate-ovate, oblique at an 
angle of about 30° with the hinge-line; length nearly twice the height; 
ante-byssal margin oblique, curving into the long, shallow sinus; base 
broadly curved ; posterior end acutely recurved. 
Left valve gibbous above, convex below. Right valve unknown. 
Hinge-line straight, greater than the height of the shell. 
Beak a little in front of the anterior third of the hinge directed forward, 
rising above the cardinal line. Umbo narrow and gibbous, subtending a 
very acute angle. 
Anterior end small, limited by a well-marked and oblique byssal depression ; 
extremity acute. The distance from the byssal sinus to the cardinal margin 
is one-half the greatest height of the valve. Wing joining the body one- 
fourth its length above the posterior end; the shallow furrow and fold defin¬ 
ing its limits are not strongly marked ; margin obliquely truncate; extremity 
not produced. 
Test thin, marked by radii which are very fine and undulating on the 
body and wing, while they are obsolete on the anterior portion; these are 
cancellated by fine concentric striae, which on some portions are fasciculate, 
and very conspicuous on the anterior end. 
Interior unknown. 
The specimen described has a length of 36 mm., height 20 mm., and 
liinge-line about 23 mm. 
This species bears considerable resemblance to P. Eucrate, but its anterior end 
is proportionally narrower, and it may also be distinguished by the absence of 
a continuous angularity along the body, the more abrupt recurving of the post- 
basal margin, the more oblique truncation of the wing, and the less conspicu¬ 
ous surface markings. It differs from P. Spio in its more gibbous umbo and 
