520 GEOLOGY OF THE DENVER BASIN. 



The three metacarpals represented in fig. 86 were found together in 

 position, near the remains of the hind limb here described. 



Another larger species is based upon the nearly complete pelvis, with 

 various vertebrae, and some other parts of the skeleton. The most striking 

 feature of the pelvis is the fact that the ilium, ischium, and pubis are firmly 

 coossified with each other, as in recent birds. This character has been 

 observed hitherto among dinosaurs only in the genus Ceratosaurus, described 

 by the writer from the Jurassic of Wyoming. The present pelvis resembles 

 that of Ceratosaurus in its general features, but there is no foramen in the 

 pubis. 



CRETACEOUS MAMMALS. 



In addition to the varied reptilian fauna now known from the Ceratops 

 beds, the many small mammals recently discovered in this horizon are 

 worthy of special mention. All are low in type and diminutive in size, 

 and among them, so far as at present determined, there were no represent- 

 atives of the carnivores, rodents, or ungulates, that form so large a proportion 

 of the mammalian life in the succeeding Tertiary period. In figs. 87 to 92 

 (p. 521), are given illustrations of a few of the mammalian fossils already 

 described bv the writer from the Ceratops beds. They were all found in 

 Converse County, Wyo. 



The small mammals represented by these remains and all others 

 known from this horizon appear to have been either monotremes or mar- 

 supials, the true placental mammals not being known until the Tertiary. 



In this brief review of the vertebrate fauna of the Ceratops beds, only 

 a few of the principal forms have been mentioned, and those which are 

 most characteristic. The large number of well-preserved specimens now 

 known from this horizon show conclusively that this vertebrate fauna is 

 very extensive, and includes so many groups of animals that, taken 

 together, they establish beyond reasonable doubt the Cretaceous age of 

 the period in which they lived. 



PAET IV. 

 CENOZOIC FOSSILS. 



The remaining horizons represented in the Denver Basin by vertebrate 

 remains may be briefly treated, as the fossils they contain are better known 

 and the succession of the important types are more clearly understood. 



