EXPLANATION OF PLATE I.

FIG. 1. Dinicthys Newberryi Clarke. Right lower mandible.

FIGS. 2, 3. Palæoniscus Devonicus Clarke. Scales. Fig. 2, × 2; Fig. 3, × 10. FIGS. 4, 5, 6. The same. Cranial plates. ×2.

FIG. 7. Pristacanthus vetustus Clarke. Spine.

Ad nat.

EXPLANATION OF PLATE II.

FIG. 1. Ceratiocaris Beecheri Clarke. Showing three abdominal segments and the telson spines. Ad nat.

FIG. 2. Ceratiocaris simplex Clarke. Carapace. Ad nat.

FIG. 3. Echinocaris Whitfieldi Clarke. Carapace.

Ad nat.

Caudal plate with two telson spines. Ad nat.

FIG. 5. Beyrichia Dagon Clarke. Side view. x 20.

FIG. 4. The same.

X 20.
x 20.
Ad nat.

Side view. X 12.

FIG. 8. Goniatites Lutheri Clarke.
FIG. 9. Goniatites Astarte Clarke.

FIG. 10. The same. Front view. X 12.
FIG. 11. Orthoceras aciculoides Clarke. X2.

FIG. 12. Orthoceras filosum Clarke. Ad nat.

FIG. 13. The same. Opposite side of the same individual.
FIG. 14. The same. A younger example. Ad nat.

FIG. 15. Orthoceras Stebos Clarke. X 12.