444 GEOLOGICAL SUEVEY OF THE TEREITORIES. 



European Eocene and Cretaceous are not represented on this continent 

 so far as known. (2.) That the flora found below the remains of a Cre- 

 taceous fauna more nearly resembles the Tertiary flora than it does that 

 of the European Cretaceous. (3.) That the flora of the Fort Union beds 

 is undoubtedly Miocene. 



These facts are confirmatory of my previous conclusion, " that a Ter- 

 tiary flora was contemporary with a Cretaceous fauna in the transition- 

 period of the Eiocky Mountains." If a flora below the Cretaceous of New 

 Mexico resembles a Tertiary one, how much more probable is it that the 

 floras of the Lignites of Colorado and Wyoming are such, as they are 

 known to be of later age than tbose of New Mexico, and to be at the 

 summit of the Cretaceous series, as indicated by animal remains. And 

 if the flora of the Fort Union beds be Miocene, that of the identical horizon 

 in Colorado must be Miocene also ; and if the vegetation below this flora 

 be so distinct from it, what is more probable, according to the evidence 

 adduced by Dr. Newberry, than that they are Eocene, as maintained by 

 Mr. Lesquereux ? That such should be the case is in harmoney rather 

 than in conflict with the facts presented by tiae existing life of the earth, 

 where we have the modern fauna of the northern hemisphere contempo- 

 rary with a partly Eocene and partly Mesozoic fauna in the southern. 



Prof. J. W. Dawson, in his late interesting annual address before 

 the Natural History Society of Montreal, thus comments on the above 

 conclusion.* He says that the mixture of Mesozoic animals with Terti- 

 ary plants " depends on the general law that in times of continental 

 elevation newer productions of the land are mixed with more antique 

 inhabitants of the sea." * * " Thus it must have happened that the 

 marine Cretaceous animals disappeared first from the high lands and 

 lingered longest in the valleys, while the life of the Tertiary came on. 

 first in the hills, and was more tardily introduced on the plains." Were 

 the Mesozoic reptiles of the Fort Union and Bitter Creek beds marine or 

 even aquatic in their character, their co-existence with a Tertiary flora 

 would, indeed, be quite explicable on Professor Dawson's view. But 

 they are in the most important and diagnostic species — the Binosauria — 

 terrestrial in their habits, and in several cases vegetable feeders, browsing 

 on the very foliage in which theip bones were touud enwrapped. 



SECTION II. — THE VERTEBEATA OF THE FOET UNION 'CEETACEOUS OF 



COLOEADO. 



DINOSAUEIA. 

 AGATHAUMAS, Cope. 



Proceedings of the American Philosophical Society, 1872, p. 482. 



The characters of this genus are derived from the typical species A. 

 sylvestris, which is represented by dorsal and lumbar vertebrse, and an 

 entire sacrum, with the ilia — one nearly entire — ribs, and a number of 

 bones, the character of which has not yet been positively ascertained. 

 One of these resembles the proximal part of the pubis ; others, portions 

 of the sternum, &c. 



On eight, and perhaps nine, vertebrae anterior to the sacrum, there is 

 no indication of the capitular articular face for the rib. This facet is 

 found, as in Crocodilia, at or near the base of the elongate diapophyses. 

 The centra are slightly concave posteriorly, and still less so on the ante- 

 rior face, with gently convex margins. The neural canal is very small, 



'May, 1874, p. 9. " 



