DEVONIAN FAUNAS. 37 
Oo 
ORTHOTHETES PANDORA (Bill.). 
Plate LII., Fig. 8. 
See, also, pp. 367 and 380. 
1867. Streptorhynchus chemungensis var. pandora Hall, Pal. N. Y., 
vol. IV., p. 68, pl. 4, figs. 11-19, pl. 9, figs. 18-25, 27. 
Some imperfect specimens of Orthothetes from the Greenwood lake 
locality may quite certainly be referred to the species O. chemungensis 
or some variety of it. Members of this,species are characterized by 
the nearly-flat pedicle valve, with straight hinge-line usually equaling 
the greatest width of the shell, with the cardinal extremities varying 
either way from rectangular, and often with a more or less distorted 
beak. The brachial valve is more convex than the other. Both 
valves are marked by fine, radiating coste, which increase by inter- 
calation and by bifurcation. The New Jersey specimens agree most 
closely with the illustrations of the variety pandora and may be re- 
ferred to that form without much doubt. 
CHONETES ARCUATUS Hall. 
Plate LI., Fig. 21. 
iSGre \Chonecves ancuata lal, Pale iN:) Yu vols DV. p. iid sol 20; 
figs. 7 a-f. 
Description.—Shell semi-elliptical or semi-circular in outline, the 
hinge-line straight, about equaling the greatest width; cardinal ex- 
tremities rectangular. Pedicle valve strongly convex, with a slight 
mesial flattening or depression, depressed toward the cardinal ex- 
tremities. In the internal casts the hinge-line is apparently crenu- 
late, the crenulations doubtless representing the bases of cardinal 
spines. A constricted line runs parallel to the front and lateral 
margins of the valve at a little distance from the margin, converging 
posteriorly to the beak; within this line the surface of the valve is 
somewhat elevated above the outer portion, the elevation being more 
conspicuous near the cardinal margin. Extending forward from the 
beak for about one-third of the length of the valve there is a low 
