August 5, 1898.] 



SCIENCE. 



149 



only fossil plants ; the invertebrate collec- 

 tors notice only their own favorites, and, as 

 both classes are numerous, the extinct ver- 

 tebrates are too often overlooked or only 

 peculiar and striking specimens secured. 

 Thus the most valuable evidence as to the 

 age of strata is neglected, and the decision 

 rendered has so frequently to be reversed. 

 This neglect is not confined to field work 

 alone, where fossil vertebrates should be 

 found, but too often extends to the litera- 

 ture of the subject. 



Let me illustrate this by a short quota- 

 tion from a well-known work : 



" The Jurassic system, which is so largely 

 developed in Europe, containing the remains 

 of huge swimming and flying reptiles * * 

 is but sparingly represented in American 

 geology, and none of the gigantic vertebrates 

 have as yet been found here."* 



The above extract may fairly be taken as 

 representing the information on the subject 

 known to the authors, or at least to the edi- 

 tor when this work was published. It is, 

 moreover, a fair sample of much that has 

 since been written about the Jurassic for- 

 mation of this country and its fossil con- 

 tents, especially by those not familiar with 

 this subject, but whose work in allied fields 

 should at least have made them acquainted 

 with the main results of our vertebrate 

 paleontology, which had become a part of 

 the world's scientific knowledge. 



For example, at the time the above work 

 was published, one of the most fruitful 

 horizons of vertebrate fossils ever discov- 

 ered had been known for several years in 

 the Jurassic of the West. Many tons of 

 gigantic fossil vertebrates had been col- 

 lected from several localities, and the prin- 

 cipal forms described and figured, while the 

 illustrations had been reproduced even in 

 text-books. Moreover, the Jurassic horizon 

 in which these and other remains were 



*Geology of the Black Hills, by Newton and Jen- 

 ney, edited by G. K. Gilbert, p. 151, 1880. 



found had been definitely determined and 

 named the Atlantosaurus beds, and a geo- 

 logical section showing their position and 

 characteristic genera had been published 

 several times. The fossils thus discovered 

 embraced mammals, birds, reptiles and 

 fishes, nearly all of well-marked Jurassic 

 types. 



Since 1880, when the statement I have 

 quoted was made, other discoveries have 

 followed in rapid succession, and the Juras- 

 sic vertebrate fauna of the West is now 

 known to be a most rich and varied one, 

 far in advance of that from any other part 

 of the world. More than one hundred and 

 fifty species of extinct vertebrates, some of 

 them represented by hundreds of specimens, 

 have been brought to light, and over ooe 

 hundred of these have already been de- 

 scribed, and the more important have been 

 refigured and republished in various parts 

 of the world, including text-books, so that 

 anyone with even an elementary knowl- 

 edge of the subject can see that they are 

 Jurassic in type. Nevertheless, a number 

 of American geologists whose studies have 

 kept them in other fields still appear to be 

 ignorant of nearly all that has been made 

 known about vertebrate paleontology in 

 this country during the last quarter of a 

 century, and seem to think that the Juras- 

 sic formation here is of small importance, 

 and that its area should be restricted rather 

 than enlarged. 



Another of my reviewers was G. K. Gil- 

 bert, editor of the work from which I have 

 just quoted. Whether he intended his re- 

 marks on my paper to be taken seriously is 

 not clear. Apparently he wished to start 

 an academic discussion on correlation, and 

 under the circumstances this would prob- 

 ably have led from the Rocky Mountains 

 to the Mountains of the Moon, one of his 

 latest fields of investigation. If he is 

 really in doubt about the methods of cor- 

 relation of vertebrate fossils he can per- 



