ACROTRETA DEPRESSA (Walcott)
Figs. 3 and 3a. Top and side views of an elevated ventral valve.
Fig. 3b. Cast of the interior of a dorsal valve.
Fig. 3c. Cast of the interior of a ventral valve.
NISUSIA ALBERTA (Walcott)
Fig. 4. A cast of the exterior surface showing bases of surface spines.
Fig. 4a. A compressed valve.
PHILHEDRA COLUMBIANA (Walcott)
Figs. 5 and 5a. Top and side views, greatly enlarged. (Very rare).
SCENELLA VARIANS Walcott
Fig. 6. Top view of a specimen with the apex nearer the center than usual.
STENOTHECA WHEELERI, new species.
Fig. 7. Side view of the type specimen. (Comparatively rare).
HYOLITHELLUS FLAGELLUM (Matthew)
Fig. 8. A long curved specimen.
Fig. 8a. A slender nearly straight specimen.
HYOLITHELLUS ANNULATA (Matthew)
Fig. 9. A large specimen with a group of small tubes adjoining it.
Fig. 9a. Enlargement of a portion of the specimen represented by figure 9. The small tubes are much like those of Hyolithellus flagellum.
