DEVONIAN AND MISSISSIPPIAN FAUNAS 103 



known from 200 feet of beds between 300 and 500 feet below the 

 summit of the entire series. 



JUNCTION OF THE EASTERN CONTINENTAL AND INTERIOR CONTINENTAL 



PROVINCES 



As has been indicated in the previous discussion of the faunas of 

 the Eastern Continental and Interior Continental Provinces, the time 

 of the establishment of a path of communication between the two was 

 at the very opening of the Upper Devonian, when the Cuboides fauna 

 found its way into the East, but the relations of the lowan faunas with 

 those of the East is not such as to suggest an entirely unobstructed 

 intermingling of faunas even after this communication was finally 

 established. Schuchert has suggested in his paleogeographic maps' 

 that this communication was by way of a narrow and somewhat 

 tortuous strait, the "Traverse Strait," which passed from southeastern 

 Iowa in a general northeasterly direction, across Illinois through the 

 Lake Michigan basin to northern Michigan. Within the limits of this 

 strait occur the Devonian beds near Milwaukee, Wis., and those of 

 the Grand Traverse region of Michigan, where there is a greater com- 

 mingling of eastern and western forms than elsewhere, as might be 

 expected under the circumstances. The waters of this strait were 

 separated from those of the Eastern Continental basin by the compara- 

 tively narrow Kankakee peninsula. 



THE WESTERN CONTINENTAL PROVINCE 



The Devonian strata of the Western Continental Province occur 

 at various localities in the Great Basin region, and their faunas have 

 been described by Walcott in his Paleontology of the Eureka District.^ 

 One hundred and eighty specifically identified forms are recorded, of 

 which 61 are new and 119 are identified with already known forms. 

 The composition of the previously known portion of the fauna is as 

 follows : 83 species are identical with forms from the Eastern Conti- 

 nental Province, including New York, Michigan, and the Ohio Valley, 

 the other 36 being known from Iowa and other parts of the Interior 

 Continental Province. Of the eastern species 29 are found only in the 

 Onondaga fauna, 21 only in the Hamilton, and 13 only in Devonian 



I Am. GeoL, XXXII, PI. 21; also, la. Geol. Surv., XVIII, pi. 16. 

 ' Monograph, U. S. G. S., Vol. VIII. 



