4 TRANSACTIONS OF THE ROYAL CANADIAN INSTITUTE. [VOL. XI 
ea 
of Ordovician species wWas obtdineds hh addition to the material from 
these definite horizons some few fossils were collected from the drift 
at the mouth of the Nelson river and in the vicinity of York. 
Under the caption ‘‘Hudson Bay Exploring Expedition, 1912” 
Mr. Tyrrell published the results of his investigations in the First Part 
of the Twenty-second Report of the Bureau of Mines of Ontario. The 
fossils collected on the expedition had been submitted to me for examin- 
ation and a preliminary account of these remains is contained in Mr. 
Tyrrell’s report. The present paper is an attempt to present in more 
extended form a description of all the recognizable material collected 
by Mr. Tyrrell. 
Nearly all the Silurian fossils and many of the Ordovician species 
are represented by casts only: this has made the identification of the 
forms difficult, and in many cases, doubtful. In fact, had the material 
been obtained from an accessible region, much of it would have been 
thrown away as indeterminable; but the remoteness of the area and 
the desire to furnish a full account of the collection has induced me 
to carry my determinations beyond the point justified under normal 
conditions. Mistakes have doubtless occurred, and science has possibly 
been burdened with more synonyms, but I have refrained from new 
specific names in many cases where | have little doubt a new species 
is represented, and have preferred to leave the form indeterminate 
until better specimens have been found. A complete disregard of this 
doubtful material would not have done justice to Mr. Tyrrell’s work. 
It is to be understood, therefore, that this paper is an account of the 
collection and not a treatise on the fauna of the region. 
The collection contains 132 distinct forms to which possibly a dozen 
more might be added: of these, 48 are ascribed to known species, 
and 31 are new to science. The remaining 53 species are described, 
and in some cases figured, but their preservation does not justify specific 
names, although many of them are probably new. An analysis of the 
collection is given on the following page. 
The most notable feature of this list is the great preponderance of 
Gastropods and Cephalopods, and in this connection it may be noted 
that some unusually large forms occur. Phragmoceras whitneyi and 
Euomphalopterus tyrrelli, herein described, are of exceptional size for 
the genera to which they belong. 
The general aspect of the fauna of the Severn and Fawn river Silurian 
indicates an horizon comparable with the Guelph of Ontario, and the 
Ordovician species of the Shamattawa river suggest the fauna of the 
Trenton. While presenting features characteristic of the Manitoba 
Trenton, the Ontario Trenton and the Trenton of Baffin Land, our 
