454 MESOZOIC TIME. 



which end with it, and also for the appearance, during its progress, of 

 the modern types of plants. 



The name Cretaceous is from the Latin creta, chalk. The Chalk 

 of England and Europe is one of the rocks of the period. 



1. American. 



Epochs. — 1. Epoch of the Earlier Cretaceous ; 2. Epoch of the 



Later Cretaceous. 



I. Rocks: kinds and distribution. 



The Cretaceous beds occur (1) at intervals along the Atlantic Border 

 south of New York, from New Jersey to South Carolina ; (2) ex- 

 tensively over the States along the Gulf Border, thence bending north- 

 ward along the Mississippi valley, nearly or quite to the mouth of the 

 Ohio, over what was then a great Mississippi bay ; (3) through a 

 large part of the Western Interior region, over the slopes of the Rocky 

 Mountains, from Texas northward to the head-waters of the Missouri, 

 and westward through Dakota, Wyoming, Utah, and Colorado terri- 

 tories ; along, farther west, some parts of the valley of the Colorado 

 River, but not over the plateau between the Sierra Nevada and the 

 Wahsatch Range ; (4) along the Pacific Border, in the Coast ranges 

 west of the Sierra Nevada ; (5) in British America, on the Saskatch- 

 ewan and Assiniboine ; also (6) on the Arctic ocean, near the mouth 

 of the Mackenzie, and in North Greenland. On the Atlantic Border, 

 they are unknown north of Cape Cod. 



The formation has its greatest thickness — 9,000 feet, or more, — 

 in Wyoming, Utah, and Colorado. In these Rocky Mountain terri- 

 tories, it passes upward without interruption into a coal-bearing for- 

 mation, several thousand feet thick, on which the following Tertiary 

 strata lie unconformably. The lower portion of the coal series, con- 

 taining one or more coal beds, may be Cretaceous ; the rest of it is 

 beyond referred to the Tertiary. 



On the map, p. 144, the Cretaceous areas are indicated by broken 

 lines running obliquely from the right above to the left below : one 

 area crosses New Jersey ; other outcrops on the Atlantic Border are 

 indicated by the lettering Or ; an extensive area covers the Gulf 

 States ; and another, the region west of the Mississippi. The region 

 along the Gulf Border as well as the Atlantic, lined closely from the 

 left to the right, is Tertiary ; and it probably covers Cretaceous, 

 throughout. The part of the Rocky Mountain region more openly 

 lined in the same direction has a surface of fresh-water Tertiary ; but 

 Cretaceous beds, in many places at least, lie beneath. 



