28 PALEONTOLOGY OF NEW YORK. 



AVICULOPECTEN CONVEXUS. 



PI.ATK VII, FIGS. •>', 'ii. 



Pe-iinl coniv.riis, Hall, neolog-. Siii'v. N. V. : Rej). Fourth Disl., p. 2S5. 1843. 



.<4rit-u/<'/>e</oi amvexus. Hall. Pal. N. V., vol. v, pt. 1. Plates and Explanations: PI. 7, tife'K. 22, 23. 



Jan., 1883. 



Shell small, sub-orbicular, not oblique; heiglit somewhat greater tliiui the 

 length; margins regularly rouudcil. 



Left valve very convex, convexity equal to a1)out oiic-third the length of 

 the shell. Right valve not known. 



Hinge-line straight, central, length three-fifths the length of the shell. 



Beak prominent, straight, central, rounded, arching over the hinge-line ; 

 the sides of the um])o subtend a right angle. 



Ears broad-triangular, extremities obtuse-angular. Posterior ear of left 

 valve smaller than the anterior, defined by the abrupt slope of tlic umbo; 

 margin slightly concave. Anterior ear convex; margin straight; separated 

 from the umbo l)y a very deep and narrow sulcus. Byssal sinus small. 



Test marked by fine irregular radiating striag and finer regular concentric 

 lines ; the same surfiice characters are continued over the ears. The speci- 

 men is exfoliated and the radii represented in the figure are partially restored. 



Interior characters unknown. 



The original of this species has a height of 12.5 nini., length 12 mm., and 

 hinge-line 8 mm. 



The remarkable convexity of the left valve distinguishes this species from 

 all the other forms here described. Its orbicular outline, prominent beak and 

 deep anterior sulcus are also characteristic. In general appearanco tlie body 

 of the shell resembles some forms of Athyris and Meristiiia ainoiig the 

 Brachiopods, but its pectinoid character is well marked. 



Formation and locality. In the shales of the Chemung group at liockville, 

 Alleghany county, N. Y. 



