34 PALEONTOLOGY OF NEW YORK. 



over the centre of the valve, becoming obscure toward the margins. The 

 ears show the concentric strise only. 



The characters of the interior are not known. 



A specimen of the left valve measures 2-"> nun. in height, 29 mm. in length, 

 and the hinge-line 21 mm. 



This species in general expression resembles A. tenuis, hut is distinct in its 

 smaller anterior ear, more obtuse beak, orbicular form, and more irregular and 

 stronger rays. Their geological positions are widely separated. 



Formation and locality. In soft shalv beds of the Corniferous limestone, which 

 constitute the upper portion of the group, at Lapham's mill, near Victor, 

 Ontario county, N. Y. 



AVICULOPECTEN INSIGXIS. 

 PLATE I, FIG. 8; PLATE III, FIG IS; AND I'LATE LXXXI, FIG 7 



Aoicidopecten insigilis, Hall. Pal. N. Y., vol. v. \A. 1. Plates and Explanations : PI. 1. &g. s ; pi. :!. fig. 13. 



.Inn., 1SS3. 



Shell less than medium size, sub-rhomboidal, moderately oblique, about one- 

 third longer than high; basal margins rounded; anterior and posterior mar- 

 gins obtusely angular or abruptly rounded, and extending along the cardinal 

 slopes in a direct line to the beak. 



Both valves are quite convex; right valve somewhat the less convex. 



Hinge-line straight, nearly equal to the length of the shell. 



Beak obtuse-angular, prominent, directed forward, nearly central. Umbonal 

 region ample, the sides subtending an obtuse angle, and sloping more 

 abruptly to the anterior than to the posterior margin. 



Ears sub-equal, triangular. Anterior ear concave or tlat, defined by a dis- 

 tinct sulcus; margin deeply concave; extremity acuminate. B\ ssal sinus 

 deep and well-marked. Posterior ear flattened, defined by the absence of 

 the stronger radii; extremity slightly acute: margin concave. 



Test thin, marked by strong radiating COStSB, which in the left valve are 

 abrupt!} elevated and increase h\ interstitial addition: crossed by infrequent 



