52 H. S. Williams— Different tyjies of the 



(2) The Eastern Continental Area, including the New 

 York and Appalachian tracts as far south as "West Virginia, 

 and extending northwestward into Canada West and Michigan ; 



(3) The Interior Continental Area, typically seen in Iowa 

 and Missouri, extending into Illinois and Indiana, and probably 

 northward toward the valley of the Mackenzie River ; and 



(4) The Western Continental Area, best known through 

 Hague and "Walcott's studies of the Eureka, Nevada, sections. 



Each of these four areas presents sections of the Devonian, 

 which in all the details of their stratigraphical, lithological and 

 paleontological composition are different from each other. 



The Eastern Border Area. 



The typical eastern border section, as seen at Gaspe, is a 

 heavy series of arenaceous shales, sandstones and conglomer- 

 ates, gray, drab and red in color, of some 7,000 feet thickness. 

 It lies upon 2,000 feet of limestone, which holds in the upper 

 part fossils of upper Silurian age. These are regarded by 

 Billings as of Helderberg types. The first thousand feet of 

 the sandstone shows a rich flora, and, by some traces of inver- 

 tebrate fossils, is known to date back as early as the age of the 

 Oriskany sandstone. The first 5,000 feet of the sandstone rep- 

 resents the interval from the top of the Silurian to the top of 

 the Chemung series of the New York section, and the terminal 

 2,000 feet may represent the Catskill series of New York. 

 (See Logan's Report upon the Gaspe section in " Geology of 

 Canada," 1863, p. 390, etc.) The greater part of this section 

 contains very few fossils, and these are mainly plant remains. 

 In the continuation of the Gaspe sandstones on the Bay de 

 Chaleur the lower and upper beds, as I am informed by Sir 

 William Dawson, are not only distinguished by characteristic 

 plants but also by a rich fish fauna resembling that of Scotland, 

 and divisible into a lower zone with Cephalaspis, Coccosteus, 

 etc., and an upper with Pterichthys. On tracing the outcrops 

 westward across Maine and Northern New England, the coral- 

 bearing limestones of the lower Devonian appear, indicating a 

 changed condition of the seas on approaching the old Archaean 

 axis on the westward, but the outcrops, as well as the identity 

 of the fossils, are too indefinite to give a clear idea of the rela- 

 tion of this border region to the better known sections south 

 of the Adirondacks and farther west in New York State. 



The Eastern Continental Area. 



The second area, the eastern continental, is represented typ- 

 ically in New York State. From there it has been traced 

 downward along the Appalachians as far as to West Yirginia 

 (the Tennessee section assuming a closer relation to the interior 



