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PALAEONTOLOGY OF NEW YORK. 
Pterinopecten (Aviculopecten ?) STRICTUS. 
PLATE XXXV, FIG. 2; Asm PLATE LXXXI, FIG. 18. 
Pterinopecten strictus, Hall. Pal. N. Y., vol. v, pt. 1. Plates and Explanations: PI. 24, fig. 2. Jan., 1883. 
Shell of medium size, transversely semi-elliptical, not oblique; body of the 
shell ovate, length one-sixth less than the height; anterior and basal 
margins rounded; posterior margin straight. 
Left valve moderately convex. Right valve flat. 
Hinge-line straight, equal to the length of the shell, central as regards 
the transverse axis. 
Beaks obtuse, low, directed slightly forward, anterior to the middle of the 
hinge-line. Umbonal region moderately prominent in the upper part, sub¬ 
tending an acute angle. 
Ears triangular. Posterior ear much the larger, flat; margin concave; 
extremity slightly acute, obscurely defined. Anterior ear small, convex, 
defined by a well-marked groove or sulcus; margin rounded; extremity 
acute. Byssal sinus distinct in the left valve, and a deep rounded notch in 
the right valve. 
Test of left valve marked by alternating stronger and finer rounded radii, 
crossed by sharp, elevated, concentric lines of growth and more distant 
undulations, with imbricating lamellose lines. These markings are continued 
over the ears, much subdued on the right valve, and obsolete upon the 
umbo. 
Ligamental area marked by two or three furrows, and a central cartilage- 
pit. 
The specimen figured has a length of 25 mm., height 30 mm., hinge-line 
25.5 mm. 
This species is doubtfully arranged with the present group of forms. In 
some aspects it resembles P. conspectus, but is specifically very distinct. It 
might be compared with the young of some large forms of Lyriopecten or with 
Aviculopecten, but the extent of the hinge-line, and the undefined limitation 
