HATCHER: OSTEOLOGY OF HAPLOCANTHOSAURUS ra 
more reasonable conclusion when considered from the standpoint of stratigraphy 
alone. 
Hvidences as to Age Afforded by the Fauna and Flora.—As already noticed Profes- 
sor Ward has regarded the cyeads from the Atlantosaurus beds of the Freeze Out 
Hills, Wyoming, locality as indicative of a Jurassic age. 
Invertebrate paleontologists have I think been unanimous in referring the marine 
Baptanodon beds to the Middle and Upper Jura. hey have it appears been most 
frequently correlated with the Oxfordian or lower member of the Middle Odlite. 
By some however they have been placed in the Lower Oolite. Since, as has been 
shown above, there is not a little evidence in favor of considering the lowermost 
150 feet of the Atlantosawrus beds at Canyon City as the equivalents of these marine 
beds in the north the age of the latter, as determined by its marine invertebrates, 
may be taken as having a certain bearing on that of the former series. The verte- 
brates of these marine beds appear to point to a somewhat greater antiquity than 
the invertebrates, for Baptanodon, the most abundant and best known form, has its 
nearest ally in the Liassic Ophthalmosawrus of Europe, and Mr. C. W. Gilmore, who 
is engaged in a thorough and exhaustive study of the American forms, has recently 
shown that the American form was not edentulous as had been supposed and that 
it is scarcely distinguishable, at least generically, from the European Liassic genus 
Ophthalmosawrus. 
Turning now to the fauna of the Atlantosawrus beds, it is readily apparent that 
the dinosaurs offer the best, indeed almost the only reliable paleontological evidence 
as to their age. We have already called attention to the fact that Cope regarded 
the dinosaurs of the uppermost of these beds as being most like those of the English 
Odlite and we have shown that Haplocanthosawrus from the lower half of the series 
resembles most closely Cetiosawrus from the Great Oodlite near Oxford. 
Marsh was wont to correlate the Atlantosawrus beds with the Wealden which he 
regarded as of Upper Jurassic age. On just what evidence he relied for this corre- 
lation is not quite clear. Nor does a comparison of the dinosaurian faunas of these 
two horizons seem to me to warrant such correlation. While from the fragmentary 
nature of much of the material upon which the different genera and species are 
based it is clearly impossible to make satisfactory comparisons in many instances 
between the more closely related genera and species of American and European 
dinosaurs, nevertheless when comparisons of the faunas as a whole are instituted 
between the various American and European horizons most striking and important 
resemblances and dissimilarities are at once apparent. Thus while in the Aflanto- 
saurus beds the Sauropoda are the predominant forms both as regards size and the 
