20 
'Sf, leptocladu7?t^ Nord., var. sinuatum, n. var. (Plate xxvil, Fig. 
24). — Differs from the typical form in the arms being more diverg- 
ent, and in the emarginate apex. 
St. Eloiseanum, n, sp. (Plate xxvii., Figs. 9 and 9^, front and end 
view.) — Small, equal in length and breadth, smooth or finely punc- 
tate; sinus produced by the constriction an acute angle; semicells 
subhexagonal, basal and superior angles produced into two short 
processes ; bifurcate at the ends ; end view circular, margin with 
nine (usually) short processes, ends notched. Diameter, 22/^-30/*. 
Minneapolis, Minn. 
This plant has some resemblance to St, spifiosiim^ Breb., but the 
processes are less conspicuous and the apices less distended. The 
end view is entirely distinct in being circular. 
St. megacantJnim^ Lund., var. convergens, n. var. (Plate xxvil, 
Figs. 13 and \za, front and end views.) — Unlike those of the typical 
form, the aculei are convergent and sometimes cross each other, 
being set riearly at right angles with the long axis of the semicells. 
The plant is also somewhat smaller. It reminds one of St, Dickiei, 
Ralfs, but it is not so turgid, and the aculei are much longer and 
stouter. Diameter, without the aculei, 38/^-45/^. 
Minneapolis, Minn. 
St. trihedrale, //. sp. (Plate xxvii.. Figs. 20 and 20^, front and 
oblique views). — Small, punctate granulate ; semicells, in front view 
and in end view, triangular, angles rounded, sides concave, sinus 
narrowly linear. Diameter, 30/^. 
Pond, Mount Everett, Mass. 
This species, in its front view, partakes much of the appearance 
of a Cosmarium, near retusum^ Perty, and angustatum^ Nord., but 
the side and end views are distinct. The semicells are three-sided 
pyramidal forms unlike those of a Cosmarium, 
St. vestitum^ Ralfs., var. distortum, n, var. (Plate xxvii., Figs. 
15 and 15a). — Separated from the typical plant by its unsymmetrical 
form, irregularly arranged vesture, and deeply notched margins. 
Collected in the vicinity of Minneapolis, Minn, 
St. Sebaldi, Reinsch, var. spinosum, n. var, (Plate xxvii., Fig. 11). 
The spine protruding near the margin of the sides of each semi- 
cell is a peculiarity worthy of note. 
Minneapolis, Minn. 
Stfurcigerum^ Breb. (Plate xxvii., Figs. 5 and 5^, end and front 
view). — This plant is figured as a specimen of a variety. It differs 
from the many forms observed heretofore, in the triradiate arrange- 
ment and the long arms on the centre of the cells in the end view. 
The arms are usually six in number, and much shorter. 
Minneapolis, Minn. 
TOLYPOTHRIX, Ktz.— j: tenuis, Ktz. Ann Arbon Mich 
- " -dbyj. Reighard; and Plainfield, N. " '' 
Balen. 
J 
CALOTHRIX, Ag.—C. mirabilis (Dillw.) Ag. Minneapolis, 
Minn. Thuret claims this plant for his new genus Pkctonetna. 
The present plant is a true Calothrix and answers to the diagnosis of 
miraOilis, 
