LAMELLIBRA NCHIA TA. 
471 
truncate. Cardinal line straight. Anterior end short, obliquely truncate 
above, and narrowly rounded below. 
Valves of moderate convexity below and posteriorly, gibbous in the umbo- 
nal region. 
Beaks sub-anterior, prominent, arcuate and projecting above the binge¬ 
line. Cincture obscure, scarcely perceptible, except toward the base of the 
shell, where it produces a slight sinuosity in the striae and basal margin. 
Umbonal slope distinctly angular, extending to the post-inferior extremity. 
Post-cardinal slope wide, distinctly limited. 
Surface marked by fine concentric striae, which become fasciculate, and 
by strong undulations on the anterior and middle portions of the shell. 
Radiating striae sometimes mark the body of the shell, but are often obscure 
or obsolete. 
Three specimens measure respectively 10, 16 and 18 mm. in length, and 
6, 9 and 9.5 mm. in height. 
This species bears much resemblance to P. radiata , but the prevailing forms 
are smaller, the concentric undulations are much stronger and the radii are 
obscure or obsolete. This form, however, may prove to be only the immature 
condition of P. radiata. 
Formation and localities. In the shales of the Hamilton group, at Fabius, and 
on the shore of Skaneateles lake, N. Y. 
Pholadella Newbekryi. 
PLATE LXXVIII, FIG. 25. 
Pholadella Newberryi, Hall. Prelim. Notice Lamellibranchiata, 2, p. 65. 1870. 
“ “ “ Pal. N. Y., vol. v, pt. 1. Plates and Explanations: PI. 78, tig-. 25. 1883. 
Allonsma {Sedgwickia?) ‘pleumpistha, Meek. Proc. Acad. Nat. Sci., Phila, vol. 23, p. 14. 1871. 
“ ( Cercomyopsis) “ “ Pal. Ohio, vol. 11, p. 309, pi. 13, figs. 4a, b, c. 1875. 
Shell large, elongate-ovate, sub-falcate; length less than twice the height. 
Basal margin regularly curving, with a gentle sinuosity anterior to the 
middle. Posterior extremity vertically or somewhat obliquely truncate. 
