Incertae sedis

Josephine E. Tilden. American Atgae.
199. Algal concretions. Silicious sinter. Described and
by Weed. (1. c. 668, 664.)
“The stony masses found in a lower and empty basin, shown in PL IjXX3^5
are apparently quite different in nature (e. g. iron1 those in no. 197), though
formed by the incrustation of the shapes shown in Fig. 56. This basin is th«
est of the series, and if some cause had not operated to produce the death
algae, and an incrustation of the structures, before the filling up of the basin
with their silicious stems, the basin would now form only a bench, indistin-
guishable from the rest of the sinter flat above it. Fig. 3,
shows a specimen taken from this basin; the transverse section proves it to
consist of a central form similar to Fig. 2, PI. LXXXVII, covered with a mossf
coating of silica, three fourths of an inch thick, which rounds off and hides the
outlines of the incrusted pillar. This coating has a rough coral-like surface*
with clustered knobs of silica, which a lens shows to consist of delicate spicules
of glassy sinter. The deposit is firm and hard, and the aggregated masses
form a compact and solid sinter.”
Lower Geyser Basin, Yellowstone National Park.
J. E. T. 29 Je 1896.
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