40 
PALAEONTOLOGY OF NEW YORK. 
rectangular beak, and more regularly alternating rays. Both of these forms 
are remarkable for the very slight convexity of the left valve. 
Formation and localities. In calcareous sandstone of the Upper Chemung 
group, Randolph and Salamanca, Cattaraugus county, N. Y. 
LYRIOPECTEN, Hall. 
Lyriopecten parallelodontus. 
PLATE IV, FIGS. 1, 2. 
Lyriopecten 'parallelodontus, Hall. MS. for Pal. N. Y„ vol. v. 1877. 
“ “ “ Catalogue Amer. Palaeozoic Fossils, S. A. Miller. Cincinnati, 1877. 
“ “ “ Pal. N. Y., vol. v, pt. 1. Plates and Explanations: PI. 4, figs. 1, 2. 
Jan., 1888. 
Shell of medium size, sub-orbicular, not oblique; height somewhat less than 
the longitudinal diameter; margins regularly rounded. 
Right valve moderately convex. Left valve unknown. 
Hinge-line straight; anterior portion not preserved in the specimen; from 
the beak to the extremity of the posterior ear its length is one-half the 
longitudinal diameter of the shell. 
Beak obtuse, rounded, slightly oblique, anterior to the centre of the valve; 
umbonal region ample. 
Posterior ear large, broad-triangular, flat; margin straight or slightly 
concave; extremity rectangular. Anterior ear not preserved. 
Test thin, marked by about 90 regular, alternating, rounded radii, with 
concave interspaces, and crossed by fine, elevated, sharp, cancellating striae; 
these are crowded over the posterior ear, and the rays are there more 
numerous and less regularly alternating. 
The mould of the interior preserves, around the margin, traces of the 
stronger rays, and shows a moderately impressed pallial line, with apparently 
an ovate, muscular impression near the umbonal region. Cartilage-pit small, 
deeply indented. Ligamental area narrow, marked by two or three slender, 
parallel grooves, extending to the posterior extremity; and one or two 
