MeetiiKj of the American Association. — Uphani. 221 
bridge and the mouth of the creek. There are eight sections, averaging 
70 feet in hight and ranging from 200 to 2,000 feet in length. The fol- 
lowing subdivisions are recognized: 
"Moscow" shales 17 feet. 
Encrinal limestone IJ-^ feet. 
Lower shales 40+ feet exposed. 
The "Conodonf bed of Hinde, which that writer placed near the top 
of the Hamilton, is referred to the base of the Genesee. 
The lowest beds exposed are the -'Trilobite beds," in which Phaco2)s 
rana and Dalmanifes boofhi occur very abundantly. Strojyheodonta. 
nacrea is another characteristic species in these beds, which may be 
traced eastward along the lake shore to Hamburg-on-the-Lake, where 
the base of the Hamilton is exjjosed aVjout seven feet below them. 
Eight feet below the Encrinal limestone is the AtJiyris spiriferoides 
bed, where this fossil occurs almost to the exclusion of every other. 
One foot below the Encrinal limestone is the StropJieodonta demisaa 
bed, the richest fossiliferous level in this region. Sixty-two species are 
obtained from this bed, which is only about four inches thick. 
The most characteristic fossil of the Lower shales, which may proper- 
ly give its name to their fauna as a whole, is Sj)ir-ifer nincroiiatus, of 
the ordinary broad-winged variety. 
The Moscow shales (so-called, though they do not correspond to the 
shales at. Moscow) contain two distinct faunas, separated by barren beds 
7 or 8 feet thick, near the center of which, however, occurs a thin bed 
v/iih Orbiculoidea media. The fauna of the lower part of the Moscow 
shales is called the Sjiirifer consobrinus fauna: that of the upper jjart 
is the Spirifer tulliiis fauna. 
A comparison of this entire series with the faunal subdivisions of the 
Hamilton of Ontario, as given by Calvin in an early number of the 
American Geologist (vol. i, pp. 81-86, Feb., 1888), shows an interest- 
ing correspondence. Of the three subdivisions made by him, the lower 
is characterized by the ordinary form of Spirifer mucronatus, and in 
its association of fossils resembles the fauna of the Lower shales at 
Eighteen Mile creek. 
In the Genesee valley the physical conditions, and the consequent 
faunal associations, were very different. The Lower shales, having a 
thickness of 90 feet or more in the Livonia salt shaft, contain few fos- 
sils, and these are mostly unlike those found at Eighteen Mile creek: 
but the Encrinal limestone is practically identical. The greatest differ 
ence is found between the Upper or Moscow shales of the two localities. 
These at Livonia are more than 300 feet thick, and the association of 
fossils recalls that in the Lower shales of the sections at Eighteen Mile 
creek. This points to an eastward migration of that fauna, following 
the changes in physical conditions. 
Under the guidance of Mr. Grabau, a party numbering nearly a hun- 
dred visited Eighteen Mile creek on Thursday afternoon, examining 
each of its eight sections here described. 
