68 



GUIDE-BOOK OF T^E WESTERIST UNITED STATES. 



contain many fossils^ including impressions of leaves, shells of fresh- 

 water clams and snails^ and bones of dinosaurs^ described below by 

 C. W. Gilmorc.* These fossils indicate a period of transition between 

 the old Cretaceous lifcj in which reptiles were the dominant forms, 

 and the newer Tertiary life, in which the mammals, the famihar 

 class of vertebrates of the present time, predominated. The dino- 

 saurs found here are the last known representatives of their type, 

 and the mammals are primitive and inconspicuous. The plants, 

 however, are of t3'pes not greatly variant from those of the present 

 time, although the species are all different. 



Bame age. 



^ Dinosaur bones belonging to the genus 

 Triceratops (wMclx meLins "three-horned 

 face"), so named in alUision to the three 

 horns "with which the skull is armed, are 

 found in the coal-bearing rocks of the 

 Hanna Basin and other formations of the 



Over each eye was a m^sive 

 horn directed forward and terminating in 

 a long, sharp point, and the nose usually 

 bore a third but much smaller horn. (See 

 PL XI, B, p. 53<) A mounted skeleton 

 of a Triceratops in the National Museum 

 at Washington is about 20 feet long and 

 stands 8 feet high at the hips. Some 

 skulls that have been found measure 

 more than 8 feet, over one-third the 

 length of the entire animal. 

 length of head is due lai'gely to the 

 rcmai-kably bony development called the 

 frill, which projects backward over the 

 neck like a fireman's helmet. 



This great 



That 



although a 



lant 



ed 



combat appears to be shown by the 



an 



found. A pair of horns in the National 

 Museum bear witness to such an en- 

 counter. One of them has been broken 

 and has healed to a rounded stump. 

 Although Triceratops had an enormous 



'am 



than 



animal of the present 



;im 



In the 



earlier restorations of this animal 



as 



shown in the accompanying 

 skin has been represented 

 smooth and leatherv. 



as being 



but a recently 



im 



sions of the skin are preserved, shows 

 that it was made up of a series of hexag- 

 onal scales of various sizes. 



Where 



Triceratops probably lived on leaves 

 and branches of low trees or shrubs. At 

 the time these animals existed, this part 

 of the country was covered with vast 

 swamps in wliich peat accumulated and 

 wide watercourses that were constantly 

 shifting their channels, the region pre- 

 senting an appearance similar to that of 

 the Everglades of Florida, 

 waters were not too deep the region must 

 have been covered by luxuriant vegeta- 

 tion and was inhabited by great numbers 

 of the huge dinosaurs, as well as by 

 smaller crocodiles, alligators, turtles, and 

 diminutive mammals, all of whose fossil 

 remains are now found embedded in the 

 deposits of that time. 



Contemporary with the Triceratops 

 was a great duck-billed reptile related 

 to Trachodon, which was the commonest 

 dinosaur of an earlier period. An aver- 

 age-sized individual measured 30 feet 

 from the tip of its nose to the end of its 

 tail, and as it walked erect on its huge 

 three-toed hind feet the top of the head 

 was 12 or 15 feet above the ground. 

 The head was nearly a yard in length, 

 and the fore part of the skull was 

 expanded to form a broad beak that was 

 covered with a homy sheath, as in birds 

 and tuitles. This was admirably suited 

 to the pulling up of the rushes and other 

 water plants that constituted the food of 

 this great creature. These trachodont 

 reptiles lived in the swamps and rivers. 

 The webbed fincrers of the fore foot indi- 



swimmin 



deep, compressed tail must have been 

 an efficient swimming organ, and was 

 also useful as a counterbalance to the 

 weight of the bodv when the iioximal 



