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[Amr] GEOLOGY OF SOME CITIES IN EASTERN CANADA 135 
Hall ; Cyrtolites ornatus, Conrad; Modiolopsis pholadiformis, Hall, 
and M. modiolaris, Conrad, are amongst the most common forms, occur- 
ring in the above mentioned locality, and are eminently characteristic 
of this horizon in almost every locality where that formation occurs 
throughout the provinces of Ontario and Quebec: from Manitoulin 
Island to Toronto, and from Chambly near Montreal to St. Nicholas 
near Quebec city, and also along the north shore of the St. Lawrence and 
of the Island of Orleans below Quebec to near St. Joachim, thirty miles 
below Quebec. 
THE SILURIAN SYSTEM. 
The Medina formation —On Lot 28, Con. VIT. of the Township of 
Cumberland, and on Lot 21, Con. IIT., of the Township of Russell, in the 
County of Russell, Ontario, to the southeast of the city of Ottawa, there 
occur a series of bright brick-red arenaceous clay shales and marls at 
times spotted green, which have as yet yielded no fossil organic remains 
with which to enable a geologist to recognize a definite fauna and hori- 
zon. This Medina outcrop, on page 219 of the Geology of Canada 
for 1863, Sir William Logan describes as “certain red shales which were 
met with between the 21st and 22nd lot of the 3rd range of Russell,” and 
adds, that owing to the amount of drift which covers the shales it is im- 
possible to trace its distribution. There is no doubt in my mind that 
this formation is nothing more nor less than the upward extension of the 
marine sediments of the Lorraine or uppermost Ordovician strata. In 
company with Dr. Ells, the writer had an excellent opportunity of exam- 
ining a number of outcrops in the localities mentioned above, and from 
the lithological character of the rocks, as well as the evident superposi- 
tion of these red shales on the buff-weathering shales on the Lorraine, 
no other conclusion could be arrived at save that which placed them in 
the lowest subdivision of the Silurian system: the Medina formation. 
There is no evidence of any break whatever in the passage beds be- 
tween the Lorraine and the Medina of this locality. It is estimated that 
at least one hundred feet of Medina red shales occur in some of the out- 
liers to the southeast of Ottawa. Drillings taken from a well sixty feet 
deep in Russell indicate clearly that there is at least that thickness of 
the Medina on the property in question. 
This series of strata referred to the Medina formation constitutes the 
newest paleozoic sediments in the vicinity of Ottawa, and may have 
formed (been) in the Period when the old Silurian sea deposited the lime- 
stones of the Niagara-Clinton rocks of Lake Temiscaming, near the 
head-waters of the Ottawa Valley. 
