398 
PALEONTOLOGY OF NEW YORK. 
strongly developed, and becoming obsolete toward the post-inferior extremity; 
the posterior margin is distinctly doubly truncate, with the lower truncation 
vertical, and the cincture is more strongly marked. 
Formation and localities. In the shales of the Hamilton group, at Fultonham, 
Schoharie county, and at York, Livingston county, N. Y. 
Sphenotus solenoides. 
PLATE LXV, FIGS. 21-29. 
iSanguinolites solenoides , Hall. Prelim. Notice Lamellibranchiata, 2, p. 3S. 1S70. 
“ “ “ Pal. N. Y., vol. v, pt. 1. Plates and Explanations: PI. 65, figs. 21-29. 1883. 
Shell large, trapezoidal; length more than twice the height; basal margin 
nearly straight, slightly arcuate in the centre, curving toward the anterior 
end. Posterior extremity obliquely truncate. Cardinal line straight, about 
half the length of the shell, parallel to the basal line. Anterior end long, 
gradually declining from below the beaks and narrowly rounded at the 
extremity. 
Valves moderately convex below and posteriorly, becoming somewhat gib¬ 
bous in the middle and umbonal regions. 
Beaks situated about two-fifths of the length of the shell from the ante¬ 
rior end, small, appressed and incurved, rising but little above the hinge¬ 
line. Umbonal slope distinctly angular, extending to the post-inferior 
extremity. Post-cardinal slope flat or slightly concave, with an obscure fold 
along the middle, extending to the posterior extremity. Cincture indistinct, 
appearing as a flattening or slight depression, extending from the beak to 
the basal margin anterior to the middle. (This feature is frequently obso¬ 
lete, except in well-preserved specimens.) 
Surface marked by fine concentric striae, which are fasciculate, producing 
more or less distinct folds or undulations upon the anterior and middle por¬ 
tions of the shell, and bending abruptly upward on crossing the umbonal 
ridge. The posterior half of the shell, especially above the umbonal ridge, 
. 
is further marked by fine, irregular, elevated vascular lines. In some speci- 
