276 IF. C?'0ss — Denver Tertiary Formation. 



been placed in the hands of Professor O. C. Marsh for iden- 

 tification and description. The fossils have proven very inter- 

 esting and have raised a number of important problems, 

 for the solution of which the material now available is in many 

 ways inadequate. But there are certain phases of these prob- 

 lems which can be discussed now as well as at any other time. 

 Professor Marsh recognizes among the bones sent him vari- 

 ous parts of the skeletons of turtles, crocodiles, dinosaurs, and 

 of a bison. Specific determinations have not yet been made 

 except in the case of the bison, but the numerous dinosaurian 

 bones clearly indicate the presence of representatives of sev- 

 eral types within this order of extinct reptiles. Until the 

 recent discovery of " a new family of horned Dinosauria from 

 the Cretaceous " in Montana,* Professor Marsh was inclined to 

 assign some of the bones from the Denver area to types hith- 

 erto known in this country only in the Jura, while other remains 

 seemed to belong to Cretaceous forms. He now considers it 

 probable that some of the Dinosaur bones collected by Mr. 

 Eldridge may be referable to the new family, the Ceratopsidse.f 

 It is plain that the occurrence of these various animals in 

 strata later than the Laramie introduces a very puzzling ele- 

 ment into the discussion, and the first thing is to prove that 

 they actually belong to the formation in question. The extinc- 

 tion of the Dinosauria in the Cretaceous period has been a doc- 

 trine seldom questioned by any authority. If the Dinosaur 

 bones of the Denver beds do not belong there they must have 

 been transported from some earlier formation, and, although 

 unable to conceive of any method by which this transfer could 

 have been accomplished, consistent with the other factors in 

 the case, the writer has been slow in coming to the belief that 

 the Dinosaurian life continued into the Denver epoch. In the 

 paper read before the Colorado Scientific Society, in July last, 

 I stated that it seemed most probable that these Dinosaur bones 

 had been transported from Jurassic or Cretaceous strata to their 

 present resting-place. This opinion has now been entirely 

 changed, and it is firmly believed that the bones found in the 

 Denver beds belong to animals that lived in the epoch in 

 which those beds were deposited. A few facts in support of 

 this belief will be given. 



Science is indebted to Mr. George L. Cannon, Jr., of Den- 

 ver, for several interesting discoveries, the results of a zealous 

 detailed study of the vicinity of the city, continued for a num- 

 ber of years. The greater share of Dinosaurian bones thus far 

 known from the Denver beds have been found by him. In an 

 article read before the Colorado Scientific Society, in October, 



* This Journal, Dec, 1888, p. 477. f Loc. cit., p. 478. 



