170 Canadian Record of Science. 
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6 04 
Lithological characters.—The Utica terrane is essentially 
a shale formation, whence the designation ‘“ Utica shale” 
which numerous writers have applied to it. It is chiefly 
composed of shales and limestone, dark in colour and some- 
times highly bituminous. 
Whilst the uppermost measures of the Trenton formation 
are characterized by calcareous strata interstratified with 
shaly bands which increase in number and extent as we 
pass upward from the Trenton to the Utica, similarly, the 
lower measures of the Utica consist of shaly strata inter- 
stratified with calcareous or limestone bands, all of which 
are bituminous in character. 
The accompanying sketch taken at New Edinburgh, 
Ottawa, along the right bank of the Ottawa River, shows 
the character of the strata at the summit of the Trenton 
and in the basal beds of the Utica:— 
These characters of the upper Trenton and lower Utica 
point clearly to a subsidence which occurred towards the 
close of the Trenton and led to the deposition of finely 
divided muds and clays. The change in the nature of the 
sediments led to achange in the forms and characters of the 
fauna or life of this old Ordovician sea, so that new forms 
of animal life were ushered in, in these pelagic depths, 
which will be discussed later on. 
The presence of many of these organic forms led to 
considerable change in the character of the strata as we 
find them at the present day. Graptolites and trilobites 
in great abundance characterize the Utica, and the shales 
are highly impregnated with bituminous materials from 
