U PALAEONTOLOGY OF NEW YORK. 



20 nun. Another individual has a height and length of 27 mm., and hinge- 

 line 10 mm. 



This species differs from A. fasciculatus in its comparatively larger anterior 

 and smaller posterior ears, while the shell is less full behind, and the fasciculate 

 surface has not been observed. In A. formio the posterior ears are much 

 larger, and the surface is distinctly reticulate. In A. scabridus the beaks are 

 more rounded, the wings more extended, and the surface quite different. Some 

 forms of A. duplicatus and A. rugastriatus resemble this species ; but the posterior 

 ears of those species are larger, the anterior pair wider, and the surface 

 markings characteristic. 



The specimen, figure 13, plate 7, from the Chemung group is very nearly 

 related to this species. A careful examination reveals the following differ- 

 ences. A. llys is less oblique in outline, radiating stria) less distinctly rounded, 

 inclining to angular, distance between them greater than the striae themselves; 

 the evidence of the implantation of intermediate strife is obscure ; the 

 concentric lines are more distant and sharper, leaving the radii in the cast 

 distinctlycrenulatc. 



Formation and localities. In the Hamilton group at Fultonham, Schoharie 

 county ; shore of Cayuga lake ; and Darien, Genesee county, N. Y. 



AVICULOPECTEN LAUTUS. 

 PLATE III, FIGS. 16, IT. 



Aviculopecten lautus, Hall. Pal. N. V., vol. v. ]>t. 1. Plates and Explanations: PI. 3. figs. 16, 1". 



Jan., 1883. 



Shell obliquely ovate, height equal to the length, valves depressed, convexity 

 of right and left valves sub-equal. 



Hinge-line straight, length about one-fifth less than the height of the 

 shell, or m some specimens longer, extending as far as the anterior margin 

 of the valve. Beaks depressed, obtuse, anterior to the centre of the hinge- 

 line. 



Ears sub-equal, triangular, Hat, mucronate at the extremities, margins 



