498 



MESOZOIC ERA— AGE OF REPTILES. 



Coal. — Conditions seem to have been especially favorable for the 

 accumulation and preservation of the abundant vegetation. Next to 

 the Carboniferous, by far the largest coal-fields of the United States 

 and of British America belong to the Cretaceous, and especially to this 

 horizon. The most important of these Cretaceous coals are the follow- 

 ing : 1. A large field covering the greater portion of Western Kansas 

 and Eastern Colorado. 2. Another valuable field in New Mexico, of 

 almost equal size. 3. Still another of greater size in Dakota, and ex- 

 tending northward far into British America. These are, all of them, 

 on the Plains* 4. On the Plateau a valuable field covers nearly the 

 whole of the Laramie plains in Wyoming, and stretching to the border 

 of Utah. The area of these coal-fields of the Plains and Plateau region 

 is not known, but must be enormous. Some of the fields are also of 

 extraordinary richness, the seams being often fifteen to twenty feet 

 thick. They almost rival the great fields of the Carboniferous, already 

 described. On the Pacific border there are several fields, which prob- 

 ably belong to the same horizon, viz. : 1. Monte Diablo and Corral 

 Hollow coal-field in California. 2. Seattle, Carbon Hill, and Belling- 

 ham Bay coals of Washington. 3. Nanaimo or Wellington coals of 

 Vancouver's Island, British Columbia. 



It is usual to call all these later coals Lignites, and to imagine that 

 they are very inferior ; but much of the Laramie coal is of good quality, 

 and hardly distinguishable in appearance from coal of the Carbonifer- 

 ous age. 



Fig. 834. 



Fig. 837. 



Fig. 836. 



Figs. 834-837.— Laramie Shells (after White}: 834. TJnio Holmesiarms. 835. Corbicula fracta. 

 836. Melania Wyomingensis. 837. Viviparus trochiformis. 



Animals. — We give a few characteristic shells, taken from White 

 (Figs. 834-837) ; but the greatest interest centers in the Dinosaurs, 

 and especially the recently discovered mammals of this epoch. As we 



