128 PALEONTOLOGY OF NEW YORK. 



ACTINOPTERIA KAl'P.V, 11. ^p. ' 

 1>I.\TK I.XXXIV, Kl<;. 13. 



Smell id' iiuMliiini si/.c. rliomboidal ; body narrowly ovate, oldiiiuc at an anuU" of 

 less tl III II \'y^\ lenj;th one-third greater than the height; anterior margin 

 oltlique, inmiilcil into the hroadly curved l)asal margin; posterior end alirnptly 

 rounded. 



Left valve dejiressed below, convex Irom the middle upward. Right valve 

 unknown. 



Hinge-line straight, equal to the height of the valve. 



Beak sul)-anterior, prominent, arching over tlic liiii^^c-linc Umlional 

 region moderately gibbous. 



Ear short, ol>li(|iie, rounded anteriorly, delined by a distinct byssal depres- 

 sion. Wing triangnlar, joining the body nearly two-thirds of the length from 

 the beak ; margin oblique, concave ; extremity produced, acute. 



Test thin, marked by fine, concentric, irregularly fasciculating striae, giving 

 an undulated a])pt'arance to the surface, and by filiform, interrupted and 

 unttulating radii, with wider interspaces, which sometimes show fine 

 intei'calated rays. The radii upon the wing are prominent and cancellated 

 by the concentric striae, and are obsolete upon the ear. 



Interior unknown. 



The specimen has a length of .'!ll nun., height "JO nun., ami hinge-line 

 l!<l nun. 



This species dilfcrs from A. epsilon, in the greater obli(iiiit\ , longer hingv-liiie, 

 and more distant radii. 



Formation and locality. In the lower member ol' tlu- Clieinuug grou[) at 

 Ithaca, N. Y. 



