PLATE CIV. 



Figures magnified 500 diameters. 



Fig. 1. TRICEKATIUM GRANDE, Bright., var. of Tr. favus fossil, Peters- 



burg, Virginia; M. J., 1853, p. 249, 4, f. 8 ; 

 Schrn. At., 82, f. 5. T. favus, 82, f. 13, 14. 

 " 2. ANTEDILUVIANUM ( Amphitetras), V. H., 109, f. 



4,5. 



" 3. UNDULATUM, (Ehrb.) Bright., M. J., 1853, p. 



248; V. H., 116, f. 7. Ditylium, Nottingham 

 deposit, Md. 

 4. INELEGANS, Grev.; T. M. S., 1866, p. 8, 2, f. 21; 



Schm. At., 81, f. 16. Santa Monica, Cal. 

 Figs^S, 6. RETICULUM, Ehrb. Mik., 33, 16, f. 13; 18. f. 50; 



M. J., 1853, p. 251, 4, f. 17. 

 Fig. 7. OBTTJSUM, Ehrb. Mik., 18, f. 48, 49; T. M. S., 



1866, p. 8. Fossil, Richmond, Virginia. 

 KAINII, Schultze ; Bull. Tor. Bot. Club, PI. 89, 

 f. 6, March, 1889. Artesian well, Atlantic 

 City. 

 " 9. DNDULATUM, Ehrb., (Virg.), M. J., 1853, p. 250, 



4, f. 13; V. H., 116, f. 13, var. Deposit, Pe- 

 tersburg, Virginia. 



Figs. 10, (17). BIQUADRATUM, Janisch, Schrn. At., 98, f. 4 and f. 



5. Leton Bank. 



11,12,14. STRIOLATUM, Ehrb. Attached to smaller forms 



of algae. Front views (11. 14) show a fine 

 but distinct hexagonal areolation. M. J., 

 1853, p. 250, 4, f. 10; T. M. S., 1854, 6, f. 3; S. 

 B. D., 5, f. 4, 6. 



13, (liii. EHRENBERGII, Griin. ; (Discoplea undulata), 



Ehrb. Fossil deposit, Nottingham, Mary- 

 land ; V. H.. 115, f. 7, 8. 



18,19. LiTHODESMiUM(Minusculum), Grun. Deposit, 



San Diego, California; V. H., 116, f. 2-4. 



