490 MESOZOIC TIME REPTILIAN AGE. 



The line of the coast on the east extended from a point in New 

 Jersey, to the southeast of New York City, across to the Delaware 

 River, whose course it followed : this river, therefore, emptied into 

 the Atlantic at Trenton, and the regions of the Delaware and Che- 

 sapeake Bays were* out at sea. From the Delaware it continued 

 southwestward, at a distance of 60 miles or more from the present 

 coast-line between New Jersey and South Carolina. It next turned 

 westward, being about 100 miles from the Atlantic in Georgia, 

 nearly 200 miles from the Gulf in Alabama, and still more remote 

 from the western Gulf shore in Texas. The Appalachians stood at 

 a less elevation than now, by GO to 100 feet. 



The Gulf of Mexico, as the map illustrates, was prolonged north- 

 ward along the valley of the Mississippi nearly to the mouth of the 

 Ohio, making here a deep bay. Into it the two great streams 

 entered, with only the mouth in common ; and probably the Ohio 

 was the larger, as its whole water-shed had nearly its present ele- 

 vation and extent, while the Mississippi area was very limited. 

 More to the westward, from the region of Texas, the Gulf ex- 

 panded to a far greater breadth and length, stretching over much 

 of the Rocky Mountain region, which was therefore so far sub- 

 merged. It reached at least to the head-waters of the Yellow- 

 stone and Missouri (which rivers were, therefore, not in existence); 

 and, judging from isolated observations in British America, the 

 waters may have continued northwestward to the Arctic seas, at 

 the mouth of Mackenzie River, where beds of this period occur. 



This Cretaceous mediterranean sea spread westward among seve- 

 ral of the elevations of the Rocky Mountain summits ; and in New 

 Mexico it spread still farther westward, over the region of the Colo- 

 rado, to or beyond the meridian of 113° W. 



By comparing the preceding map with that of the Azoic (p. 136), it 

 is seen that the continent had made great progress since the open- 

 ing of the Silurian age. But, as all this Cretaceous area was under 

 Cretaceous seas, much was still to be added to the permanent dry 

 land before its completion. 



The great Interior Continental basin, which had been a lime- 

 stone-making region for the most part from the earliest period 

 of the Silurian, was still, in its southern part, — that is, in Texas, — 

 continuing the same work ; for limestones 800 feet thick were there 

 formed. To the north of Texas, where the waters were shallower, 

 there appear to have been none of the Echinoderms, Corals, Orbi- 

 tolinse, etc. which were common in Texas. 



It has been noted that during the Triassic and Jurassic periods 

 there were no marine beds formed on the Atlantic or Gulf borders 



