176 GEOLOGY. 



Triassic belong, also, the coal fields of Eastern Virginia and North 

 Carolina. It is probable that while the conditions under which coal 

 was accumulated in all geological times were.similar, the plants dif- 

 fered exceedingly. The higher cryptogams obtained in carbonifer- 

 ous times, but in the Triassic Ferns, and especially conifers and 

 cycads, were the common forms. (Le Conte). The Jurassic was 

 eminently the age of naked seeded trees (gymnosperms), especially 

 of the Cycads, which at that time culminated m the number of 

 species and individuals. In fact, three- fourths of all the fossil Zamiae 

 and one-half the cycads known from all the geological formations, 

 are from the Jurassic. No one can look at a cycad, with its long, 

 fern-like leaves, without admiring its beauty. These vegetable 

 forms are now confined to low, moist latitudes, but for immense 

 periods of geological time they were the dominant type on what 

 are now the plains of Nebraska. Here, in those times, along 

 with tree ferns and araucarians, they made immense thickets and 

 forests. 



Animal Life. The Mesozoic was eminently a Reptilian Age. 

 All kinds of vertebrate life took on more or less of this type. Ne- 

 braska, being then a land surface throughout the Triassic and Ju- 

 rassic periods, we will omit the consideration of the animal life pe- 

 culiar to the seas. The land, however, with the peculiar vegetation 

 referred to in the preceding section, and with its warm, temperate 

 climate, was eminently adapted to the support of a land reptile 

 fauna. What this fauna was, we can only imagine from the reptilian 

 remains preserved in the deposits of these periods nearest to us. 

 Many are found in western Kansas and eastern Colorado. The 

 foothills are of Jurassic age, and are composed of clay and sand- 

 stone beds, overlaid directly by a heavy bed of the peculiar con- 

 glomerate of the Cretaceous Dakota Group. These beds, as al- 

 ready remarked, have been called Atlantosaurus beds by Marsh, 

 from the prevalence in them of huge remains of Dinosaurs. No 

 land animals of such gigantic size have ever been discovered else- 

 where in deposits of any geological age. The most important lo- 

 cality for these remains is at Morrison and Canyon City, where the 

 Atlantosaurus immanis (monstrous sized lizard) was found. Its 

 femur was eight feet four inches long, which would indicate, on the 

 principles of comparative anatomy, an animal walking on all fours 

 of over one hundred feet in length and over thirty feet in height. 

 It approximated closely in size to the limits beyond which locomo- 



