480 Wisconsin Academy of Sciences , Arts , and Letters. 
Cellulis lati-ovatis. Longitudo cellularum 2-plo latitudo. 
Aculeis brevibus, latitudine cellulae atque longitudine aculei 
equale. 
Chodat gives no measurements for his S. quadrispina but 
computations from his figures, which were magnified 800 
diameters, shows that the cell dimensions are 8.5 x 3.7, 
12.5 x 7, and 15 x 8.5 p. The alga which I have obtained 
in pure culture corresponds very closely with this, the cell 
measurements being 8.5 x 3.5, 9x4, 9.5 x 4.5, 10.5x6.5, 
11 x 6 p so that it is quite probable that this alga is the same 
as that which Chodat had in pure culture. 
Var. parvus nov. var. (PI. XXXI: Figs. 162-166.) 
Cellulis ovati-cylindricis. Longitudo cellularum 2-2.5-plo 
latitudo. Longitudine cellulae atque longitudine aculei 
equale. Dimens. cell. 5.5 x 3^ 6x3, 7x3, 8x3 p. Long, 
acul. 4.5 ad 8 p. 
The limits of this variety are quite sharply defined since 
the largest cells are as long and but slightly narrower than the 
smallest cells of longispina, the next smallest variety. 
Var. longispina (Chodat) nov. comb. (PI. XXVII: Fig. 
42; PI. XXXI: Figs. 159-161.) 
S. longispina. Chodat, 1913, p. 60: Figs. 53-58. 
Cellulis ovati-cylindricis. Longitudo cellularum 2.5-plo 
latitudo. Dimens. cell. 8. x 3.8, 8 x 4.5, 8.5 x 5, 11 x 5 p. 
Long. acul. 7.5-9.5 p. 
Since Chodat gives no dimensions for the form he named 
longispina I have again computed them from his figures and 
find them to be 8.6 x 3.5, 9.5 x 3.7, 11x4.5 p with spines 
11-14 p long. Although the spines in the form I have iso¬ 
lated are somewhat shorter the dimensions of the cells are 
sufficiently near those of S. longispina of Chodat to regard 
the two as identical. 
Var. Westii nov. var. (PI. XXXII: Figs. 177-180.) 
Dimens. cell. 16 x 4.5, 17 x 5.5, 20 x 9, 22 x 8 p. Long, 
acul. 12-16 p. 
The size of this variety approaches the variety maximum 
West and West but the largest cells in my pure cultures of 
