14 
PALAEONTOLOGY OF NEW YORK. 
20 mm. Another individual has a height and length of 27 mm., and hinge¬ 
line 16 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. rugcustriatus 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. Itys is less oblique in outline, radiating striae less distinctly rounded, 
inclining to angular, distance between them greater than the striae themselves; 
the evidence of the implantation of intermediate striae is obscure; the 
concentric lines are more distant and sharper, leaving the radii in the cast 
distinctly crenulate. 
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. 16,17. 
Aviculopecten lautus. Hall. Pal. N. Y„ vol. v, pt. 1. Plates and Explanations: PI. 3, figs. 16, 17. 
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 in 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, flat, mucronate at the extremities, margins 
