65 JOURNAL OF THE 
Although admitting much irregularity, especially on ac- 
count of the supposed gemmiferous character of Paleotrochis, 
the ones which have been considered the most characteristic 
of the fossil are the distinctly biconical forms. These, so far 
as seen, are chiefly granular quartz with more or less green 
biotite. 
It is important to note also that the dark groups of green 
biotite occur in the interior of very irregular nodules which 
have no suggestion in them of Paleotrochis. Irregular flat- 
tened lenticular masses of granular quartz with green biotite 
occur within the spherulites as well asabout them. The green 
mica is found only in the most coarsely granular groups of 
quartz. 
The following chemical analysis, made by W, F. Hille- 
brand, shows that the rock has the composition of a rhyolite 
and accords closely with the results of the microscopical 
study. 
Analysis of the Paleotrochis-bearing rock of Sam Christian 
Mine.’ 
SH bes sis) eee 
Tes biivar ni lke a OI 
Al,O, .......---» 1LL41 with a very litthewae 
Ly? © Mies eres |, 
ly: 6 Meena oe 
Mate: 2055... :. oko ee 
CaO ; 
Sc 5 
Ba ee a ee 
Nie): ee Cts eer ttle 
Ba) 2 SRN 
Naw) «seen <a 
H.,O below 105°.. 18 
“<“* above; fs -) Seb Genition) 
100°02 
Recognizing the Paleotrochis rock as an acid volcanic, full 
of spherulites, it is easy to understand the great variation in 
1 No other constituents looked for. if 
