482 
PALAEONTOLOGY OF NEW YORK 
OrTHONOTA (?) PARVULA. 
PLATE LXV, FIGS. 2,3; AND PLATE LXXVIII, FIGS. 29-32. 
Ortliondia parvula, Hall. Prelim. Notice Lamellibranchiata, 2, p. 88. 1870. 
“ “ “ Pal. N. Y., vol. v, pt. 1. Plates and Explanations: PI. 78, fig's. 29-32. 1883. 
In part iSanquinolites truncatus (Conrad, sp.), Hall. Pal. N. Y., vol. v, pt. 1. Plates and Explanations: 
PI. 65, figs. 1-6. 1883. 
Shell small, elongate, sub-trapezoidal; length three times the height. Ventral 
and dorsal margins straight and sub-parallel. Posterior extremity vertically 
or obliquely truncate below and curving forward above. Anterior end nar¬ 
rowly and regularly rounded from the cardinal margin. 
Valves moderately convex below and posteriorly, becoming gibbous in the 
middle and umbonal regions. 
Beaks at about the anterior fourth, flattened and incurved, rising very little 
above the liinge-line. Umbonal slope angular, extending to the post-inferior 
extremity. Post-cardinal slope flat or slightly concave, sometimes obscurely 
marked by a depression or fold below the middle. 
Surface marked by extremely fine, thread-like concentric strise, which are 
often lamellose on the post-cardinal slope. 
Three specimens measure respectively 14, 15 and 20 mm. in length, and 
4.5, 5 and 6 mm. in height. 
This shell was placed under the genus Orthonota on account of its long, 
straight hinge-line and absence of a lunule and any indication of external liga¬ 
ment. The two valves are frequently in conjunction as in other species of 
Orthonota. The surface markings are in no respect like 0. undulata , but do not 
differ essentially from 0. carinato. Its generic relations are still in doubt. 
Formation and localities. In the shales of the Hamilton group near Fulton- 
ham and Summit, Schoharie county; in Onondaga and Livingston counties; 
and on the shores of Seneca and Canandaigua lakes, N. Y. 
