Lamellibranchiata. 237 



AVICULOPECTEK SIGNATUS. 



Avicula ? signata, Hall. Geolog. Surv. N. Y.: Rep. Fourth Dist., p. 265. 1843. 

 Aviculopecten signatus, Hall. Pal. N. T., vol. v, pt. 1. Plates and Explana- 

 tions : PI. 7, fig. 24. Jan., 1883. 



Shell small, obliquely sub-elliptical, the longest diameter making an 

 angle of about 45 ° with the hinge-line ; height and length nearly 

 equal. Left valve depressed, slightly convex.. Right valve un- 

 known. Hinge-line straight, length more than two- thirds the length 

 of the shell, extending in front as far as the anterior margin . Beak 

 very obtuse, rounded, depressed, directed forward, situated near the 

 center of the hinge. Ears triangular, sub-equal, flat. Anterior ear 

 separated from the umbo by a sulcus ; margin convex ; extremity 

 rounded. Byssal sinus moderately deep. Posterior ear not well 

 defined ; margin slightly concave ; extremity obtuse-angular. 



Test conspicuously marked by fine, regular, lamellose concentric 

 lines, and a few irregular, radiating, indented striae. 



The original of this species is 11 mm. in length and height ; the 

 hinge-line 8 mm. 



This species is distinguished by the oblique, elliptical outline of the 

 body of the shell, the depressed, obtuse beak, and the well-defined 

 concentric striae. 



Formation and locality. In the Chemung group at Rockville, 

 Alleghany county, N. Y. 



Aviculopectek Oaroli. 



Aviculopecten Caroli, Winchell. Proceedings Acad. Nat. Sci., Phila. 1863. 

 Aviculopecten CaroU (Winchell), Hall. Pal. N Y., vol. v, pt. 1. Plates and 

 Explanations : PI. 9, fig. 5. Jan., 1883. 



Shell small, sub-circular, not oblique ; length and height equal ; 

 basal margin regularly rounded. Left valve convex, the convexity 

 equal to about one-sixth of the longitudinal diameter. Eight valve 

 unknown. Hinge-line straight, length three-fourths of the diame- 

 ter, extending nearly to the anterior margin of the shell. Beak ob- 

 tuse, prominent, central, rising above the hinge. Ears triangular, 

 nearly equal, separated from the umbo by distinct sulci. Anterior 

 ear with slightly convex margin ; extremity rounded, Byssal sinus 

 deep. Margin of posterior ear concave ; extremity abruptly mucro- 

 nate. 



The test (as preserved on a partial cast of the interior) is marked 

 by about 45 regular alternating, rounded rays with equal inter- 



