44 
PALEONTOLOGY OF NEW YORK. 
Pterinopeden suborbicularis, in some of the younger specimens, resembles this 
species in general aspect; but none of that species have shown a broad, 
ligamental area, and the ears continue to increase with the growth of the shell. 
Formation and localities. In shales of the Hamilton group at Monteith’s 
Point, Canandaigua lake, Ontario county; Moscow, Geneseo and York, Liv¬ 
ingston county; and in the shale and Encrinal limestone, along Lake Erie 
shore, Eighteen-Mile creek, Erie county, N. Y. 
Lyriopecten interradiatus. 
PLATE II, FIGS. 1-4 ; and PLATE L XXX II, FIG. 5. 
Lyriopecten inteiradiatus, Hall. Pal. N. Y., vol. v, pt. 1. Plates and Explanations: PL 2, figs. 1-4. 
Jan., 1883. 
Shell large, longitudinally very broadly elliptical; transverse axis somewhat 
oblique to the hinge-line; height about one-ninth less than the length; 
margins full and regularly rounded. 
Valves about equal in dimensions. Left valve depressed, moderately 
convex. Right valve flat, or slightly concave below, becoming convex 
towards the beak. 
Hinge-line straight, central to the body of the shell; length less than two- 
thirds the longitudinal diameter of the shell. 
Beak of left valve obtuse, not prominent, directed forward, situated about 
one-third the length of the hinge-line from the extremity of the anterior ear. 
In the right valve the umbo is often flat, and the angle subtended by its 
sides is acute, caused by the deep byssal sinus. 
Posterior ears narrow-triangular, distinguished from the gradually sloping 
sides of the umbo by their flatness and finer markings; margins concave; 
extremities mucronate. Anterior ear of the left valve smaller, triangular; 
margins concave; extremity rectangular. Anterior ear of the right valve 
convex, triangular, truncated at the extremity; separated from the umbo by 
a deep angular sulcus, and a broad longitudinal semi-elliptical byssal sinus, 
which forms an indentation in the lateral outline of the body of the shell. 
Test of the left valve marked by about 40 strong rounded rays with 
