LAMELLIBRANCHIATA. 121 



ACTINOPTERIA AURICULATA, 11. Sp. 

 PLATE LXXXIV, FIG. 15. 



Shell small, rhomboidal ; l^ody ovate, oblique at an angle of more than 45'^ 

 with the hinge ; length about one-fifth greater than the height ; anterior 

 margin rounded to the sinus ; base gently rui-ved ; posterior margin abruptly 

 recurved. 



Left valve regularly convex below, gibbous above. Right valve unknown. 



Hinge-line straight, greater than the height of the valve. 



Beak anterior to the middle of the hinge-line, acute, prominent, arching over 

 the hinge. Umbonal region abruptly gibbous, subtending an acute angle. 



Ear large, straight above, limited by an abrupt vertical byssal depression ; 

 extremity rounded. Wing small, not strongly defined, joining the body 

 two-thirds of its length below the beak ; margin concave ; extremity 

 produced. 



Test marked by concentric striae, and about twenty somewhat strong, 

 sharp radii ; this ornamentation is also continued on the wing and the ear. 



Interior unknown. 



The specimen is 10 min. in length, 6 mm. in height, hinge-line 7 mm. 



This species resembles A. perstrialis in form, but difiers in the larger ear, 

 abrupt vertical byssal depression, shorter wing and coarser radii. 



Formation and localitij. In the Chemung group at Lawrenceville, Tioga 

 county. Pa. 



AcTINOPTERIA DELTA. 



PLATE XXni, FIG. 3. 



Acfhioplei-in delta, H.\Li,. Pal. N. Y , vol. v. pt. 1. Pliite.s and Explanations: PI. 28, tig-. 3. Jan.. 1SS8. 



Shell of medium size, rhomboidal ; body broad-ovate, oblique at an angle of about 



60° ; height less than three-fifths the length ; anterior margin rounded, 



curving into a defined sinus ; base broadly curved ; post-basal side abruptly 



rounded. 



16 



