224 • THOMAS H. CLARK 



reasons we should use, in general, easy-flowing lines such as those 

 which characterize Schuchert's paleogeographic maps. 



The St. Lawrence Channel was open for the greater part if not 

 all of Onondaga time. The northern shore line from Montreal 

 west to Lake Huron is drawn in accordance with the conclusions 

 reached above. In Dunbar's map,^ this shore line is placed much 

 farther south, probably through inadvertence, there being no reason 

 for showing a land area on the site of the long east and west outcrop 

 in New York. The irregularities in the shore line around the Great 

 Lakes and to the south^ are omitted, for some seem not to be well 

 founded, and none is essential. The western shore Hne of southern 

 Appalachia is removed somewhat eastward, in order not to em- 

 barrass the coral faunas of western Tennessee and Kentucky. 



The "New Jersey Strait" is not represented on the present map, 

 but instead there is a wide sea-way traversing southern and central 

 New England. In general, a wide strait is preferable to a narrow 

 one, and, in particular, it seems unlikely that there was a sea-way 

 across New Jersey, on account of the great thicknesses of delta depos- 

 its which accumulated there only a few epochs later. If there is an 

 error in the position of this New England Channel, it is probably 

 that it Hes too far south. 



From the Onondaga onward, Appalachia began to rise and to 

 extend northward. By the close of Onondaga time, it had effected 

 a junction with the island across the New England Channel, 

 thereby closing it. It has been supposed that the St. Lawrence 

 Channel was closed at the end of the Onondaga, and this is probably 

 correct. The rising Appalachia was later to shed the enormous 

 amount of sediment comprised in the Upper Devonian deltas of the 

 northern Appalachian region. With the St. Lawrence and the 

 New England channels closed, subsequent invasions of European 

 faunas must be explained as having come by way of the Arctic 

 rather than by the Atlantic Ocean. 



The Cincinnati dome is not represented as an island upon this 

 map, because it was probably covered much, if not all, of the time 



'Carl O. Dunbar, "Stratigraphy and Correlation of the Devonian of Western 

 Tennessee," Geol. Surv. Term., Bull. 21 (1919), Fig. 3B. 

 ^ See Stauffer, op. ciL, PI. 14. 



