1898] SOME WEST AMERICAN THERMAL ALG IOI 
Stratum thin, scarlet (miniatus ) ; filaments somewhat straight ; 
sheath visible under high powers ; trichomes fragile, frequently 
interrupted, neither attenuate nor curved, not constricted at 
joints, lu in diameter; articulations quadrate or a little longer 
than broad; dissepiments not or rarely visible. 
In overflow from small hillside spring. Water tepid. Between 
Middle and Upper Geyser Basins, Yellowstone National Park. 
J.E.T. 2 Jl 1896. 
This species is near P. luridum and P. purpurascens. From 
the former it differs in not having trichomes constricted at joints. 
From the latter it differs in not having strongly tortuous fila- 
ments nor granulated dissepiments. It is also to be distinguished 
from both by the color of the stratum and of the trichomes and 
the length of the articulations. 
OscILLATORIA PRINCEPS Vauch. Hist. Conferv. d’eau douce 
190. pl. 15, f. 2. 1803. Tilden, Am. Alg. Cent, II. no. 187. 
1896. (PL. IX, fig. 19.) 
Stratum dark green or black; trichomes 16—19» in diameter ; 
‘Pex slightly attenuate and shortly arcuate ; articulations 4.5- 
5-5# long; protoplasm finely granulate; apical cell convex ; 
calyptra none. 
at (2) Forming a black thick floating mass in mountain stream 
a ot spring ; gradually running out, and replaced by 
cane . distance of fifty feet from vent. Temperature five 
near oe Spring 42°C., fifty feet from spring 38°C. Mountains 
Nati &z Perces creek, Lower Geyser Basin, Yellowstone 
ripe Park. J. F.T. og Je 1806. 
ns dark green velvety mass fringing edge of small 
nk, T creek where a hot spring flows out just underneath the 
Surface - of water one inch below surface 19°C. On 
Stone ee - Near Emerald Pool, Upper Geyser Basin, Yellow- 
tonal Park. J. E. T. 3 Jl 1896. 
Am putsTORIA TENUIS Ag. Alg. Dec. 2:25. 1813. Tilden, 
ates Cent. II. no, 190. 1896. (Pl. LX, fig. 20.) 
um Black or purplish (atro-violaceus); filaments dilute 
