66 CONTKIBUTIONS TO DEVONIAN PALEONTOLOGY. [bull. 244. 
The Hollowing Run section, lower Augusta Township, North- 
umberland County Pa., about at intersection of 76° 50' and 40° 45'.* 
The Leroy section, composed of four shorter sections at Gulf Brook, 
near Leroy, Bradford County, Pa., Granville Center at South Moun- 
tain, the opposite side of the Towanda Creek from Leroy, andTowanda 
Narrows, about 6 miles east of Leroy. The general position of the 
section is near the intersection of 76° 45' W. and 41 45' N. 
The Tioga section, along Tioga River, near village of Tioga, Tioga 
County, Pa., near the intersection of 77° 10' W. and 41 c 50' N. 
The Mansfield ore bed section, about 8 miles south of Mansfield, 
Tioga County, Pa. 
The Canoe Camp section, several miles still farther south on east side 
of Tioga River. 
The Armenia Mountain section, two miles west of Troy, in Bradford 
County, Pa. 
The last four sections belong together, though their actual con- 
tinuity is not established by continuous sections. The system of 
recording and designating the faunules and their bionic values here 
adopted is the same as that employed and more elaborately defined in 
Bulletin United States Geological Survey, No. '210, "The Correlation 
of Geological Faunas.' 1 
INTRODUCTION. 
By E. M. Kindle. 
The two methods of correlation of stratified rocks which are in use 
are based upon the comparison and similarity of faunas and of rock 
sections. In their application one or the other of these methods is 
generally employed to the partial or entire neglect of the other. The 
paleontologist and the geologist have usually not the time or the 
inclination to make a minute study, respectively, of all the faunules 
or beds of a section. The two methods are supplementary, and 
neither can yield its best service in correlation when used independ- 
ently of the other. 
The ideal section from the standpoint of both correlation and fauna] 
geology should show the thickness and character of the rocks and the 
lists of the species at each locality. The close relationship of the bio- 
logical and the physical elements of the section are expressed in the 
accompanying sections. Both the paleontological and the stratigraph- 
ical data have been combined in the same section. The relation of the 
several elements of the faunas or the species to the section is indicated 
by the range and comparative abundance of each species. 
The comparison of faunas can not give the most satisfactory results 
for purposes of correlation until the history of the faunas compared is 
fairly well known. Changing conditions of environment constantly 
