LAMELLIBRANCHIA TA. 
399 
mens similar markings appear, in a subdued degree, over the anterior portion 
of the shell. Interior unknown. Ligamental area narrow. 
Eour specimens measure respectively 28, 33, 38 and 42 mm. in length, 
and 12, 14, 16 and 16.5 in height. The largest specimen observed has a 
length of 72 mm. and a height of 28 mm. 
This species is distinguished by its long anterior end and peculiar ornamen¬ 
tation on the posterior half of the shell. 
Formation and localities. In the shales of the Hamilton group, Sherburne 
creek near Sherburne, Hamilton, Bellona and on the shores of Canandaigua and 
Cayuga lakes, N. Y. 
Sphenotus contractus. 
PLATE LXVI, FIGS. 1, 3-9, 11-13, 15 (10, 16, 17, 19?); AND PLATE XCIV, FIG. 2. 
Cypricardia contmcta, Hall. Geol. Surv. N. Y., Rep. Fourth Dist., p. 292, t. 139, fig-. 4. 1843. 
In part Sanguinolites riffidus (White and Whitfield), Hall. Prelim. Notice Lamellibranchiata, 2, p. 44. 
1870. 
“ “ “ “ “ Pal. N. Y., vol. v, pt. 1. Plates and Ex¬ 
planations: PI. 66, figs. 1-19. 1883. 
Shell ranging from small to large size; trapezoidal, wider behind; length 
more than twice the height; basal margin nearly straight, scarcely con¬ 
stricted in the middle and gently curving to either extremity. Posterior 
extremity oblique, somewhat doubly truncate. Cardinal line straight, long, 
nearly parallel to the basal margin. Anterior end short, abruptly declining 
from the beak and narrowly rounded below. 
Valves of moderate convexity, except in the upper portion and umbonal 
region, where they are gibbous. 
Beaks sub-anterior, small, appressed and closely incurved over the hinge¬ 
line. Uinbonal slope distinctly angular, extending to the post-inferior 
extremity. Post-cardinal slope Hat, marked along its centre by a distinct 
fold, which reaches to the posterior end, producing an extension of the mar¬ 
gin, leaving a more oblique truncation above than below. Cincture without 
distinct limitation, producing a flattening above and a slight depression 
below the middle of the valve. 
