108 Review of Recent Geological Literature. 
elation, but rather confirms that part of Mr. Croll'sastronomicaltheory 
since the time required for the glacial epoch in both cases is not far 
from ten thousand years. 
Mr. Upham's survey of the evidence of local, continental or regional 
elevation in North America, in Appendix A. is interesting and valuable ; 
and as a result he accepts the Lyellian hypothesis that such fluctua- 
tions have caused not only changes in the distribution and area of land 
over the surface of the earth, but also have been the prime cause of 
the glacial epoch. "Briefly stated, the condition and relation of the 
earth's crust and interior appear to be such that they produce in con- 
nection with contraction of the earth's mass, depressions and uplifts of 
extensive areas, some of which have been raised to bights where their 
precipitation of moisture throughout the year was almost wholly snow, 
gradually forming thick ice-sheets; but under the heavy load of ice 
subsidence ensued, with correlative uplift of other portions of the 
earth's crust; so that glacial conditions may have prevailed alternately 
In the northern and southern hemispheres, or in North America and 
Europe, and may have been repeated after warm interglacial epochs." 
This is a broader and a more flexible application of the Lyellian hy- 
pothesis, and appeals to well-known terrestrial movements, influenced 
by terrestrial agencies. It goes further than the assumption of eleva- 
tion, in that it accounts for the elevation. As a theory for terrestrial 
glaciation it is not new, but the hypothetical manner of application and 
distribution of the supposed cause for such glaciation appears to be 
new, and as such deserves the attention of glacialists and physicists. 
The Bulletin of the American Museum of Natural History, vol. ii. No. 
2, was issued in March 1889 and fully maintains the high reputation of 
the series to which it belongs. The geological papers are by Prof. R. 
P. Whitfield, four in number, and are respectively entitled Observations 
on some imperfectly known fossils from the Calciferous sandrock of Lake 
Champlain, and descriptions of several new forms; Additional notes on 
Asaphus canalis, Conrad; Description of a new form of fossil Balanoid 
Cirripede, from the Marcellus shale of New York; and Note on the faunal 
resemblance between the Cretaceous formations of New Jersey, and those>of 
the Gulf states. 
Discovery of Cretaceous Mammals by Professor 0. C. Marsh. {AY>pen- 
dix to American Journal of Science, July, 1889.) The great break in 
the geological history of mammals, due to the apparent absence of mam- 
malian remains in any authentically recognized deposits of Cretaceous 
age, has long been one of the strangest and most inexplicable of the facts 
confronting the student of palaeontology. Small marsupial mammals 
are known from numerous specimens in the Triassic and Jurassic, 
both of Europe and America. Mammals, more or less specialized, 
and fully diS'erentiated into distinct orders, swarmed in the forests and 
haunted the lake margins in the earliest Tertiary ; mammals must 
have existed during the Cretaceous. It was during the Cretaceous 
that all the difTerentiation seen among the earlv Tertiary mammals 
