HISTORICAL REVIEW OF OPINION. 



431 



He reiterates his statement that " Witli the exception of one species of 

 Axinoea, one of Nuculana, and one or two of Odontobasis, no species 

 usually regarded as of n)arine types have been found in any of the 

 strata of the Laramie group," and ijronounces all statements in conflict 

 with this, even though made by himself, as the result of errors in strati- 

 graphical determination. He also repeats the remark (p. 51 ) that " among 

 all the invertebrate fossils which have yet been discovered in the strata of 

 the Laramie group, none of the types are distinctively characteristic of 

 the Cretaceous period according to any hitherto recognized standard," 

 and he adduces a mass of facts in support of the view previously ad- 

 vocated, " that the Laramie is really a transitional group between the 

 Cretaceous beneath and the Tertiary above (p. 52)." 



In the sixth volume of Prof. Oswald Heer's great work on the Arctic 

 fossil flora,' the eminent Swiss paleontologist approaches this question 

 of the age of the American plant-bearing beds. As might be expected, 

 he strongly defends Mr. Lesquereux's position as to the Eocene age of 

 the Laramie group against the arguments of those who would refer it 

 to the Cretaceous. He characterizes the doctrine that the Dinosaurs 

 became extinct at the close of the Mesozoic as a " dogma," and, speaking 

 of Cope's A(jathaumas, says that it by no means proves that a Tertiary 

 flora was contemporary with a Cretaceous fauna, " for a single animal 

 does not make a fauna any more than one plant makes a flora," and 

 instances the animal forms also found by Cope and others at the same 

 horizon, which agree better with the Eocene faunas of France. 



In the supplement to the third volume of the reports of Lieutenant 

 Wheelers Survey, which bears date 1S81, Mr. John J. Stevenson again 

 discusses the age of the Laramie group, adhering as warmly as ever to 

 his previous views. As in his former reports, notwithstanding frequent 

 denials in the meantime, he still insists (p. 154) that " farther north in Col- 

 orado characteristic Fox Hills fossils were obtained in abundance near 

 the summit of the fully recognized Laramie:'' This and the further state- 

 ment (p. 154) that "the fauna is either marine or brackish- water" are 

 both contrary to the definition of the Laramie group as laid down by ^ , 

 Dr. White, and indicate that this geologist had been unable to distiu- ( ' 

 guish the marine from the brackish-water strata. In his final con- 

 clusion that the Laramie merely constitutes the upper part of the Fox 

 Hills group (p. 158), Mr. Stevenson seems to be sustained by no other 

 authority, even the stratigraphical geologists, fully aware of the con- 

 formity of the deposition, not being willing to regard a marine and a 

 brackish-water deposit as a single homcgeneous group. 



The Third Annual Eeport of the United States Geological Survey, 

 published in 1883, contains Dr. White's "Review of the non-marine 

 fossil moUusca of North America," illustrated by 32 plates, 22 of which 

 are devoted to species of the Laramie group, all of which are described 



^|^M. 



(^ 



' BeitrUge znr mioceneu Flora von Nord-Canada. Zurich, 1880, pp. 6-10. 



