208 The American Geologist. March, 1891 
Dr. Croll, dissatisfied with terrestial causes, boldly reached out 
and sought in the varying eccentricity of the earth's orbit a suffi- 
cient cosmical cause. It is not too much to say that no speculation 
connected with this subject has been more fruitful of result or 
more stimulating to investigation than this. Captivating and fas- 
cinating, however, as it was at first, all the argument of its 
able author could not establish it on a secure base and he was led 
by his enthusiasm into the adoption and promulgation of views 
which, in cold light, now appear somewhat extreme. His theory 
is no longer accepted, at least by most American geologists, being 
contraiy to all the positive evidence afforded by glacial phenomena 
on this continent, but like many others it will ever remain a splen- 
did monument to the reach and power of the intellect of Dr. 
Croll, by whose death theoretical geology loses a strong and able 
investigator. 
Through the Instrumentality of Dr. Hans Reusch, Dr. 
Winchell's work entitled "Shall We Teach Geology?" is being 
translated and republished in the Dagbladet, Christiania. It will 
subsequently be used by Dr. Reusch in his classes in his "Semi- 
nary of Geology," in the University of Christiania. 
Discovery of Fish Remains in Lower Silurian Rocks. 
At a meeting of the Riological Society of Washington on Feb- 
ruary 7th, 1891, Mr. Charles D. Walcott, of the U. S. Geological 
Survey, announced the discovery of vertebrate life in the Lower 
Silurian (Ordovician) strata. He stated that "The remains were 
found in a sandstone resting on the pre-Paleozoic rocks of 
the eastern front of the Rocky mountains, near Canon City, Col- 
orado. They consist of an immense number of separate plates of 
placoganoid fishes and many fragments of the calcified covering 
of the notochord, of a form provisionally referred to the Elasmo- 
branchii. The accompaivying invertebrate fauna has the facies of 
the Trenton fauna of New York and the Mississippi valley. It ex- 
tends upward into the superjacent limestone and at an horizon 
180 feet above the fish beds, seventeen out of thirty-three species 
that have been distinguished are identical with species occurring 
in the Trenton limestone of Wisconsin and New York. 
"Great interest centers about this discover}* from the fact that 
we now have some of the ancestors of the great group of placo- 
derm fishes which appear so suddenly at the close of the Upper 
Silurian and in the lower portion of the Devonian groups. It 
also carries the vertebrate fauna far back into the Silurian and in- 
dicates that the differentiation between the invertebrate and verte- 
brate t} T pes probably occuxTed in Cambrian time." 
Mr. Walcott is preparing a full description of the stratigraphic 
section, mode of occurrence and character of the invertebrate and 
vertebrate faunas for presentation at the meeting of the Geologi- 
cal Society of America, in August, 1891. 
