REVIEWS 379 
the head of Frobisher Bay. The fossils are well preserved and many 
of them are now in the U. S. National Museum. The paper gives a 
brief summary of the geology of the region as gathered from reports 
by those who have either visited it or have examined collections from 
it. The Lower Silurian fossils so far collected are of Trenton and 
Utica age, and strata containing these faunas are widespread in eastern 
Arctic America. So far as known they rest upon the pre-Cambrian 
rocks and are overlain by beds of Niagara age. Of the 72 species 
known from the locality of Silliman’s Fossil Mount 28 are restricted 
to it. Of the remaining 54 species, 41 are found in the Manitoba- 
Minnesota-Wisconsin region and 17 in the New York-Ottawa region. 
A comparison of the 54 species found elsewhere with those from 
definite stages in Minnesqta shows that 1o are found in the Birds-eye 
(Lowville), 17 in the Black River, 38 in the Galena, and 11 in the 
Cincinnatian. 
The close resemblance of the Minnesota Galena to the Silliman’s 
Fossil Mount formation may in large part explain the close identity of 
the faunas. In the summary, page 175, the author says: ‘‘ The Baffin 
Land fauna had an early introduction of Upper Silurian genera in the 
corals Halysites, Lyella and Plasmopora. In Manitoba similar con- 
ditions occur in the presence of Halysites, Favosites, and Diphy- 
phyllum. The Trenton fauna of Baffin Land shows that corals, 
brachiopods, gastropods, and trilobites have wide distribution and are 
therefore less sensitive to differing habitats apt to occur in widely 
separated regions. On the other hand the cephalopods and particu- 
larly the pelecypods, indicate a shorter geographical range. The 
almost complete absence of Bryozoa in the Baffin Land Trenton con- 
trasts strongly with the great development of these animals in Minne- 
sota and elsewhere in the United States.” 
The paper is a valuable addition to our knowledge of the Ordo- 
vician faunas of eastern Arctic America. 
R. D. GEORGE. 
The Freshwater Tertiary Formations of the Rocky Mountain Region. 
By W. M. Davis. Proceedings of the American Academy 
of Arts and Sciences, Vol. XXXV, No. 17, March, 1900. 
In this very timely paper Professor Davis gives voice to a growing 
change of opinion regarding the specific mode of origin of the most 
