January, 1900. 
Teller— The Hamilton Formation. 
47 
The Hamilton Formation at Milwaukee, Wisconsin. 
By EDGAR E. TELLER. 
The geological formation displayed at the quarries of the Mil- 
waukee Cement Company, belongs to that period known as the 
Hamilton, and is a part of the Devonian Age, so named by Alur- 
chison from the exposures in North and South Devon, England, 
for all of the strata which intervene between the upper siluriaii 
and the carboniferous rocks. The Age has been identified over a 
wide geographical extent of the earth's surface, being known to- 
extend to the Continent of Europe ; it is found in Russia, at the 
Cape of Good Hope, in China, and on the American continent, 
where is found the best development of the Age, as well as the 
most perfectly preserved organic remains ; also the greatest variety 
both in genera and species. 
The group name is that given by Vanuxem from its exposures 
at Hamilton^ Madison County, New York. Of its organic re- 
mains he says: "It abounds in fossils, such as shells, corals, tri- 
lobites, fucoids, and a few plant remains resembling those of ter- 
rene origin. In organic remains it is the most prolific of all the 
New York rocks." 
The late James Hall, thei\ the geologist of the State of Wiscon- 
sin, in his report on the geological survey of the state, 1861, con- 
siders what he refers to the Upper Helderberg and the Hamilton 
groups, in one article. He says "we find a compact fossiliferous 
limestone and above it some shaly beds, likewise with fossils. 
These calcareous and shaly beds are clearly identified by their 
fossils, belonging to the age- of the Upper Helderberg and Hamil- 
ton groups of New York." Referring to the organic remains he 
says : 'The fossil remains of these beds are chiefly Spirifci\ 
Stropheodonta, Orthis and Atrypa, a few LaincUibranchiatc shells 
have been observed, a single species of Gyroccras, and one of 
Gojuphoceras/' Inasmuch as in the preceding article he had re- 
ferred what is now recognized as the Lower Helderberg Group 
of Wisconsin, to the western extension of the Onondaga. Salt 
group of New York state, it would probably be natural'that he 
should look among the succeeding formations for the equivalent 
of the Upper Helderberg, and as that formation in New York 
is exceedingly rich in organic remains of those genera noted in 
Wisconsin, on a cursory examination it is probably not strange 
