PLATE XXVIII. 



Figures magnified 500 diameters. 



Fiiis. 1, 2. SCHIZONEMA RABfosissiMA, Ag. Syst., Fig. 1. A frond, natural 



size; S. B. P., II, p. 79, 59, f. 369, Sm.. Sp. T., 



No. 47s. 

 " 3,4. SMITHII, 3, the frustule, 4, frond, natural size, 



Ag. Syst,, p. 10, K. B., 27, f. 5, V. H., 15, f. 4. 



" 5. f>. GREVILLKI. 5, frond, nat. size and frustule 5 ?, Ag., 



K. B., 5, f. 1 ; 26, f. 4, 8. B. D,, 5S, f. 364, Prit., p. 

 928, 8, f. 3S. 

 " 7,8. IMPLICATUM, 7, frond, nat. size ; 8, frustnles, S. B. 



D., 5!), f. :i(i7, Sin. Sp. T., No. 471. 

 " 9, 10. CRUCGIEK. frond, nat. si/.c, and frustule ""," S., 



B. D., 51), f. 354, Frit., 92s, Y. H., Hi. f. 1, '_!. 

 11, 12. CUMOIDES, ( Frustulo "'/", and frond, nat, size), Ag., 



8. B. D., PI. 57, f. 358, V. H., 16, f. 3. 

 Fig. i:;. AMERICANTM, Grun., V. H., 15, f. 35, (=8. tenne, 



var. ) 



14. DIVERGENT, 8. B! D., PL 57, f. 363, Sin. Sp. T., No. 



465, V. H., 15, f. 10, probably a var. of S. Smithii. 



15, (19.) GOMPHONEMA, coxsTRicTUM, var. Minor., Ehrb., K. B., 13, f. 



1-3, Rab. 8. D., 8, f. 12, 8. B. D., II, 98, 28, f. 

 236. 



16, (20). CAPITATUM, Ehrb. Mik., 16, 3, f. 37 ; 17, 1, f.'51, 



Rab. 8. W. D., 8, f. 15, 8. B. D., PI. 28, f. 237, 

 Sm. Sp. T., 177 and 665. 



17, IS. AUGUR, Ehrb. Mik., 17, 1, f. 55; 9, 1, f. 40, K. 



B., 29, f. 74, Rab. 8. D., 8, f. 19, V. H., 23, f. 29, 

 probably a var. of G. Acuminatum. 

 Fig. 21. CAPITATUM, Ehrb., coinp. Fig. 16 and 20. 



Larger form. 



" 22. Aci'MiNATUM, var. latk-eps, Ehrb. 



" 23. " var. laticeps. 



" 24. var. trigonocephalum, Ehrb. 



" 25. var. turris. Ehrb. 



" 26. var. coronata, Ehrb. 



" 27. var. intermedia, Grun., Ehrb. 



Mik., 16, 3, f. 34; 17. ~2. i. 37; 16, 2, f. 43, Sill. 

 .1.. var. July, ]S42, p. 323, 3, f. 6, K. B., 13, f. 3, 

 S. B. D., 2S, f. 23,s ; M. .!., 1S54, p. 99, 4, f. 13, 

 Prit., S87, 13, f. 23; 8m. Sp. T., No. 175. 



