Morgan Expeditions. 122 
extend downward, and somewhat obliquely backward, across the valve; 
but it becomes less and less perceptible toward the ventral margin, 
toward which the slope, for nearly the whole height of the valve, near 
the middle, is only slightly curved; toward the front, the slope is much 
stronger and it becomes concave in front of, and beneath, the beaks. 
Commencing. at the anterior margin, the surface rises at a moderately 
strong angle for one-fifth the shell length, more or less, when, the 
angle of ascent becoming gradually less, it continues to rise with very 
little curvature toward an oblique line, extending across the valve from 
the posterior side of the beak to the lower posterior extremity of the 
shell. Along this line the valve rounds over toward the dorsal and 
posterior margins, quite gradually in the lower part, but more and more 
abruptly near the beak, the curve, from the point of greatest convexity 
of the valve toward the posterior end of the hinge margin, being abrupt 
and slightly sigmoidal. Exterior surface unknown. Length, 22™™; 
height, 14™™; convexity of single valve, 5.5™™, 
This species is founded on a single specimen, a very per- 
fect internal mould of the left valve; but one or two much 
smaller specimens, probably referable to the same species, 
were also obtained from Ereré. From the Devonian sand- 
stone of Ereré, Prov. of Para, Brazil; «ussociated with 
Spirifera Pedroana, ete. 
(Named after my friends, Mr. Fred. Pond, American 
Consul at Para, and his brother, Mr. Thos. Pond, to whom 
I am indebted for a thousand favors. C. F. H.) 
Edmondia Sylvana, sp. nov. 
Shell small; length a little more than one and one-half times the height; 
outline apparently sub-elliptical. Valves moderately convex and nearly 
symmetrical, most prominent in the umbonal region. Beaks small, sub- 
central and obtuse in the moulds, incurving very little and hardly pro- 
jecting above the plane of the hinge, between which and the apices of 
the beak is quite a space. The dorsal margin is regularly curved, and 
rounds down on each side of the beak to the anterior and posterior 
margins, of which the former seems to be the narrower, and is more 
regularly rounded than the latter; ventral margin nearly straight along 
the middle. The surface of the valves arches very strongly and quite 
regularly from the beaks to the ventral margin, while the curvature along 
the antero-posterior diameter is moderate and nearly regular. Length, 
17™™; height, 10™™; convexity of single valve, 4™™, 
