120 
PALEONTOLOGY OF NEW YORK. 
Actinopteria tenuistriata, n. sp. 
PL.ATE LXXXIV, FIGS. 5, 6. 
Shell small, sub-quadrate; body short-ovate, oblique at an angle of 60° with 
the hinge; length about one-fifth greater than the height; anterior margin 
below the sinus nearly vertical, and then making a broad curve along the 
base; posterior margin broadly curved. 
Left valve regularly convex below the middle, gibbous on the umbo. 
Right valve smaller, nearly equally convex. 
Hinge-line straight, a little greater than the height of the valve. 
Beaks at about the anterior third of the hinge-line, prominent, obtuse, 
rising above the hinge. Umbonal region gibbous and ample, subtending 
nearly a right angle. 
Ear small, defined by a distinct sinus and byssal depression, rounded at 
the extremity. Wing small, triangular, joining the body below the middle of 
its length, not strongly limited ; margin gently concave ; extremity acute. 
Test thin, marked by fine concentric striae, and filiform radiations with 
wider interspaces, which are marked by extremely slender intermediate 
striae. On the anterior side the radiating lines are finer, and on the cardinal 
margin of the wing they are stronger. The right valve is marked only by 
elevated concentric striae, and the wing by fine radiations, which become 
stronger toward the cardinal margin. 
One specimen has a length of 16 mm., height 13 mm., and hinge-line 
14 mm. 
This species is distinguished from A. perstrialis by its erect and more nearly 
quadrate form, shorter ear, less extended wing with less concave margin, and 
more distant, finer striae. 
Formation and locality. In the lower part of the Chemung group at 
Ithaca, N. Y. 
