98 The American Geologist. Augnr^t, 1892 
dorsal and ventral margins subparallel. Dorsal edge nearly 
straight, likewise the posterior, the two lines meeting at an angle 
of about 120°. Postero-ventral angle sharply curved, the 
ventral side gently convex and rounding almost uniformly up 
into the anterior outline. 13eaks terminal, small, projecting, 
slightly above the hinge line, scarcely incurved. Umbonal ridge 
strongly convex, extending toward the postero-ventral extremity 
in a slightly curved direction, so that the slopes on the anterior 
and ventral sides are more abrupt than on the opposite sides. 
Point of greatest convexity a little in front of and above the 
middle. 
Interior with the hinge plate rather wide and strong, and the 
anterior edge, for a short distance beneath the beaks, much 
thickened inwardly. Muscular scars large, situated about mid- 
way in the postero-cardinal half of the shell, the two lobes united 
by a narrow neck, the upper one oval in shape and about one- 
third as large as the more nearly circular lower one. 
The posterior extremity is more produced and more narrowly 
curved than in the other species referred to this genus. 
Foruiatlon and locality: Lower limestone of the Trenton 
formation at Minneapolis, Minnesota. A single specimen only. 
This was collected by Mr. J. C. Kassube, and by him donated to 
the museum of the Geological and Natural History Survey of 
Minnesota, where it is now to be found under the Mas. Reg. No. 
5526. 
Cypricardites terminalis, n. sp. 
Plate vri, Fig?. 8-10. 
Shell of medium size, moderately ventricose, extremely oblique, 
with the beaks terminal, rather small, strongly incurved, and pro- 
jecting but little above the hinge line. Umbo full, and the whole 
surface neatly rounded. Outline obliquely acuminate-ovoid, with 
the anterior end narrowly rounded and projecting scarcel}', if at 
all, beyond the beaks, from which the margin slopes backward 
with a gentle curve into the base ; posterior end Inroad, uniformly 
rounded; cardinal margin straight, about three-fifths as long as 
the diagonal length of the shell, rounding into the posterior mar- 
gin. Surface with faint wrinkles of growth and probably with 
finer concentric lines. Shell substance thin. Hinge plate rather 
narrow, with two long posterior and two or three short cardinal 
teeth in each valve. The latter are difficult to see because of the 
