﻿NO. 7 



SMITHSONIAN EXPLORATIONS, I926 



43 



determining the correlation of the beds exposed in that region with 

 those of the New York deposits. The country intervening has been 

 subjected to much erosion and is moreover covered under a heavy 

 deposit of glacial material, so that the strata under study are nowhere 

 displayed. This correlation was accomplished on the basis of a bed 

 immediately above the Encrinal limestone, shown in figures 48 and 49, 

 which contains the exact fauna that is carried in one of the zones 

 of the section in western New York at East Bethany. The strata 

 at Thedford and Arkona have been separated into a three-fold divi- 



FiG. 50. — Rock Glen, Arkona, Ontario. The Encrinal limestone here forms 

 a small falls due to relative resistance in contrast to that of the soft shales 

 above and below. (Photograph by E. R. Pohl.) 



sion according to their fossil content. The lower beds, or as they are 

 locally called, the Olentangy shales, are composed of fine gray shales 

 which easily weather into a soft mud used in making pottery, and 

 carry thin lenses of hard crystalline limestone composed throughout 

 of masses of beautifully sculptured fossil remains. Several large 

 exhibition slabs, besides much other material, were returned to the 

 Museum from these beds. The middle division includes the so-called 

 Encrinal limestone which is made up of an innumerable mass of 

 crinoid remains, and a three-foot bed of shale which is referred to as 

 the " coral bed " on account of the large number of fossil corals 



