Lamellibranchiata. 229 



AVICULOPECTEN CANCELLATUS. 



Pecten cancellatus, Hall. Geolog. Surv. N. Y. : Rep, Fourth Dist. 1843. 



Not Aviculopecten cancellatulus, McCoy. 



Pecten Hallianus* d'Orbigny. Prodrome de Palseontologie, vol. i, p. 87, No. 



768. 1847. 

 Aviculopecten sub-cancellatus, Hall. Pal. N, Y., vol. v, pt. 1. Plates and 



Explanations : PI. 7, figs. 12, 14-19. Jan., 1883. 



Shell small, broadly ovate, oblique; height a little greater than the 

 length ; anterior lateral margin full and rounded ; posterior lateral 

 margin, below the ears, gently curving. Right valve regularly con- 

 vex, sloping somewhat abruptly to the posterior ear. Hinge-line 

 straight, equal to two-thirds the length of the shell. Beaks, anterior 

 to the middle of the hinge-line, well-defined, obtuse. Posterior 

 ear small, undefined, the lateral margin concave, not projecting. 

 Anterior ear marked by a deep sinus, with a sulcus extending to the 

 beak ; lateral margin rounded. 



Test marked by fine, regular, rounded, radiating lines, crossed 

 by regular, sharp, concentric striae, producing an evenly cancellate 

 surface. The posterior ear is marked by the concentric striae 

 with obscure radiating lines ; the anterior ear is rugose from the 

 prominence of from four to six strong rays. 



The original of this species is 20 mm. in height, 19 mm. in 

 longitudinal diameter, and the length of hinge-line 12 mm. 



This species is distinguished from A. duplicatus and A. rugcestria- 

 tus by the less rugose surface, smaller size and different outline. The 

 form of the ears and byssal sinus is very similar to A. duplicates, but 

 differs in the regular reticulate surface ; that species is also a com- 

 paratively longer shell. It is in shape more like A. rugcestriatus. 



Formation and localities. In the middle members of the Chemung 

 group, at Philipsburg and Rockville, Alleghany county ; Oonewango x 

 Cattaraugus county, and near Westfield, Chautauqua county, N. Y. 



Aviculopecten ^quilatebalis. 



Aviculopecten mquilateralis, Hall. Pal. N. Y., vol. v, pt. 1. Unpublished . 



Shell of medium size, transversely ovate, erect, equilateral ; height 

 equal to the length; lateral and basal margins regularly rounded ; 

 upper anterior and posterior margins extending in nearly a straight 



* This name was proposed by d'Orbigny as a substitute for Pecten cancellatus, 

 a name pre-occupied by Phillips for an Oolitic fossil. The latter is probably a 

 true Pecten, and there seems to me no sufficient reason why the original name 

 may not be retained. Avicula cancellata, Phillips, Palaeozoic Fossils, is probably 

 not an Aviculopecten. 



