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PALEONTOLOGY OF NEW-YORK. 
Var. A. Strcptorliyiiclms pandora. 
PLATES IY & IX. 
Streptorhynchus pandora : Billings, Canadian Journal, p. 226. 1860. 
•< “ Billings, Geology of Canada, p.369. 1863. ' 
Compare Streptorhynchus [Sir oph omen a] woolworthana, Hall, Tenth Report State Cabinet, p. 8. 1857. 
“ “ “ “ Hall, Pal. New York, Vol.iii, pa. 192, pi. 16, 
f. 1 & 2. 1859. 
This shell, in its symmetrical form is somewhat semioval, the length and 
width being about as four to five. A well-formed specimen, of one inch 
in length, measures one and a quarter inches in width : hinge-line 
equal to the greatest width of the shell, and forming right angles 
with the sides, which are usually nearly straight; the front broadly 
rounded : cardinal extremities sometimes a little salient, and some¬ 
times rounded. Ventral valve convex on the umbo, the greatest con¬ 
vexity being at the apex, from which the surface slopes in a regular 
plane to the sides and middle of the shell, becoming slightly concave 
below the middle and along the front : area large triangular, extending 
the entire length of the hinge-line, and inclining over the dorsal valve 
at an angle of about 110°. The foramen has been large, about twice as 
wide at the base as the height, and is closed by a convex deltidium. 
Dorsal valve moderately convex, a little flattened towards the cardinal 
extremities, and curving towards the sides and front; area narrow and 
linear. 
Surface striated by numerous fine strongly elevated striae, which are 
increased by bifurcation and interstitial additions, and crenulated by 
fine closely arranged concentric striae. 
The interior of the ventral valve is marked by strong dental lamellae 
and a broad flabellate muscular impression, which, in well-preserved 
specimens, shows the cordiform imprint of the adductors, and a short 
low mesial septum in the upper part. 
The interior of the dorsal valve preserves deep dental sockets, with 
thick socket-plates which support the duplicate cardinal process, each 
division of which is grooved at the extremity. There is likewise a small 
