Hinge line about one-third the width of the shell. Cardinal area very narrow and inconspicuous.
Brachial valve not known. Pedicle valve showing a lightly impressed muscle scar and a distinct median septum, which latter is traceable about one-half the length of the shell.
Surface showing distinct growth lines and rather indistinct radiating markings. These latter can hardly represent the surface spines, but suggest them.
Horizon and locality.—Amherstburg dolomite, Stony Island Dry Cut, Livingston Channel, Detroit River, near Trenton, Michigan.
Loxanena inculta n.sp.
Plate II, Figs. 7 and 8
Shell tapering gradually to a high spire; apical angle 35°. Six or more volutions which are moderately convex or somewhat flattened on the outer surface but rather abruptly curving on the lower side of the whorl. Aperture subelliptical. Surface marked by strong regularly elevated striae, which turn gently backward from the suture and then forward, completing the curve before the periphery of the whorl is reached and below which they have been preserved.
Horizon and locality.—Amherstburg dolomite, Stony Island Dry Cut, Livingston Channel, Detroit River, near Trenton, Michigan.
Callonema perlata n.sp.
Plate III, Figs. 1 and 2
Shell depressed turbinate; spire low, consisting of five or more volutions which increase in size gradually and are oval in cross-section. Apical angle 138°. Umbilicus large and shallow. Suture moderately depressed and marking the outer margin of the preceding whorl.
Surface marked by medium to coarse striae of growth, which pass obliquely outward from the suture, continue over the periphery, from which they curve gently backward, and then disappear in the umbilicus. The coarseness of the striae increases with distance from the apex of the spire.
