56 
AUG. F. FOERSTE 
the beak, is more distinctly concave. Posterior to the beak there 
is no trace of an umbonal ridge, the convexity of the valves 
increasing toward the cardinal margin. The posterior margin 
of the valves is similar to that of a relatively short Ctenodonta. 
8. Ctenodonta (?) cataractensis Sp. nov. 
Plate XIII, fig. 4 
Left valve 7.3 mm. long, 5.5 mm. high, and 1.5 mm. deep. 
General outline elliptical, with the longer axis in a horizontal 
direction, but with the beak sufficiently elevated to add a slight 
triangularity to the elliptical outline. The beak is about 3 
mm. from the anterior margin. The outline posterior to the beak 
is convex as far as the posterior angle of the valve. The outline 
anterior to the beak is almost imperceptibly concave. The 
ventral outline is evenly convex along the greater part of its 
length, this convexity increasing toward the extremities of the 
valve, where the outline is most rapidly rounded. The maximum 
depth of the valve is about 2 mm. below the beak. 
9. Liospira (?) sp. 
Plate XIII, fig. 11 
Specimen with a maximum transverse diameter of 5 mm., 
consisting of at least two volutions. Evidently only a part of 
the shell is preserved, the number of additional volutions in a 
mature specimen being unknown. The spire is depressed, very 
much as in Liospira micula (Hall), from the Ordovician. The 
outer margin is narrowly rounded, also as in Liospira micula, 
and not elevated as in Pleurotomaria (?) pervetusta (Conrad), in 
which the height of the spire and of the individual volutions is 
much greater. With only a single specimen at hand it is im- 
possible to determine with confidence either its relationship to, 
or its difference fron Pleurotomaria pervetusta. Tt may be the 
apical part of the latter species. 
