Plate III. 

 Diplograptus pristis^ Hall. 



Figs. 1, 2, 3.— Siculae. X 2. 



Fig. 3a. — IS'atural size. 



Fig. 3b. — Basal cyst, x 6. 

 Figs. 4, 5, 6, 7. — Young hydrosomes. x 2. 



Ehabdosomes, with one theca each. 



Fig. 6a. — Basal cyst, x 6. 



Fig. 7a. — Basal cyst, x 4. ' 



Figs. 8, 9. — Young hydrosomes. x 2. 



Ehabdosomes, with two thecaB each. 

 Fig. 10. — Young hydrosome. X 2 . 



Ehabdosome with three hydrothecae. 

 Fig. 11. — Young primary hydrosome . X 2. 



Ehabdosome, with five thecsB. 

 Fig. 12. — Young primary hydrosome. x 2. 



Ehabdosome with seven thecse. 

 Fig. 13. — Young primary hydrosome. X 2. 



Ehabdosome with 11 thecaB. 

 Fig. 14. — Young primary hydrosome. x 2. 



Ehabdosome with 13 thecaB. 

 Figs. 15, 16. — Hydrosome with first generation of siculae.j^ x 2. 



h. — Hydrocaulus of primary rhabdosome. 

 Fig. 17. — Hydrosome with first generation of siculaB. X 2. 



The hydrocauli have grown longer. 

 Fig. 18. — do. The siculaB have begun to produce thecaB. x 2. 

 Fig. 19. — Hydrosome, with first generation of rhabdosomes . 

 X 2. 



a. — Primary rhabdosome. 

 Fig. 20. — Hydrosome with second generation of gonangia and 



siculae. x 2. • - 



Fig. 21.— do. X 2. 



Fig. 21a. — Center of hydrosome. x 4. 

 Fig. 22. — do. J^atural size. 



Fig. s. — Sicula, arrested by hydrocaulus. 



Fig. 22a.— X 2. 

 Fig. 23.— do. ^Natural size. 



Fig. 23a. — Central disc with pit. X 2. 

 Fig. 24. — Adolescent hydrosome. Katural size. 



Two generations of rhabdosomes (I and II) and one 

 of gonangia (g). 

 Fig. 25. — Central disc with two siculaB. X 4. 

 Fig. 26. — Central disc with four siculaB. X 4. 



