122 Morgan Expeditions. 



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 mm ; 

 height, 14 mm ; convexity of single valve. 5.5 mm . 



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 Erere. From the Devonian sand- 

 stone of Erere, Prov. of Para, Brazil ; associated with 

 Sftirifera Pedroana, etc. 



(Named after my friends, Mr. Fred. Pond, American 

 Consul at Pani, 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 mm ; height, 10 mm ; convexity of single valve, 4 mm . 



