348 On Eozoin Canadense. 
cise place in the series has not been determined, nor is it known 
whether the fossil extends to the two lower conformable lime- 
stone bands, or to ee calcareous zones in the unconformable 
Upper Laurentian serie 
“The Grenville zone hon limestone is in some places about 
1500 feet thick, and it appears to be divided for considerable dis- 
tances into two or = parts by very thick bands of gneiss. 
One of these bands occu- 
pies a position petite he 
lower part of the limestone, 
Fig. 2.— Section across Trembling 
Mountain e miles 
~ 
Mountain = 
Bas 
oe 
Fo 
LS 
= 
of the zone is largely com- f f par ef! f 
as r Laurentian. , e’. Second limestone. 
irregular masses of white ec. Fourtl h gneiss. l¢ s iss. 
crystalline 2 cee some ares Ener f First limestone. 
of them tw aris hird gne jf. First gneiss. 
aks Ses 
length by four or five ae They a appear to be confusedly 
placed one above another, with many ragged interstices, and 
smoothly-worn, rounded, large and small pits and sub-cyl lindri- 
cal cavities, some of them prett deep. The pyroxene, though 
it posers: compact, presents a multitude of small spaces filled 
with carbonate of lime, and many of these show minute struc- 
ture similar to that of the fossil. These,masses of pyroxene 
Spaces among them are filled with a mixture of serpentine and 
carbonate of lime. In general a sheet of pure dark green ser 
pentine invests each mass of pyroxene; the thickness of the 
serpentine, varying from the sixteenth of an inch to seve 
inches, rarely exceeding half a foot. This is followed in differ- 
ent spots by parallel waving, irregularly alternating plates 0 
page of lime and serpentine, w which become gradually finer 
= te from the pyroxene, and occasionally occupy @ 
te: tal thickness of five or six x inches. These portions constitute 
2 thu ne of gereeR appear o be the ruins of oe 
into a more or less granular mixture of cale- 
tine, the former still 
ress eo a “similar mix 
owing ewes eee : 
ee a ee ee ee ea ee 
