PLATE XV HI. 

 Figures magnified 500 diameters. 



Fig. 1. NAVICULA COLUMNARIS, Ehrb. Mik., 14, f. 23; 7, 1, f. 4; Schm. 



At,, 49, f. 1. New York, Mass. 

 " 2. EXCENTRICA, Grun.. 1860, p. 545. 1, f. 1 ; Schm. At., 



50, f. 6, 7, marine. 

 " 3. TUMESCENS, Grun., Schm. At.. 49, f. 10; ( X. fir inn 



var. ) Maine. 

 4. IRIDTS, Ehrb., K. B., 28, f. 42; Donk., B. P., p. 30, 5, 



f. 6; Schm. At.. 49, f. 2, (larger var. of N. ftrma?) 



New York. 

 ' 5. DILATATA, Ehrb. Mik., 3, f. 25, Rab., S. 1)., p. 37, 



comp. Fig. 7, typical form. 

 " 6. " COLUMNARIS, vide Fig. 1, above. 



7. DILATATA, var. Ehrb. Mik., 16, 3. f. 25; 8, 3, a., f. 9, 



Sohm. At., 49, 6, 9; Maine, Mass. 



' 8. DILATATA, Schm. At., 49, 9. Monmouth, Maine. 



" 9. BLEISCHII, Jan. and Rab., p. 9, 2, f. 10, Schm. At., 



50, f. 22, 25, n earl v related to N. excentrica. 

 " 10. AMPHIGAMPHUS, Ehrb. Mik., 6, 1. f. 20; 7, 1, f. 16; 



K. B., p. 93, 28, f. 40; Rab., S. P., p. 38, 6, f. 47; 



Schrn. At., 49, f. 31-34. Frequent, usually repre- 

 sented by smaller forms. 



