300 



formation. Iu addition to these, Barnum Brown has described from the 

 Hell Creek beds a large stegosaur. Ankylosaurus magniventris, the type 

 of a new family. We can not doubt that some day a closely related form 

 will be discovered in the Judith River beds ; and indeed, its immediate 

 ancestor may be Lambe's StereocepJialus tutus, from the Belly River de- 

 posits. 



The large herbivorous dinosaurs, the Hadrosauriche. which were ac- 

 customed to walk about on their hinder limbs only, are, according to 

 Cope's identifications, represented in the Judith River formation by about 

 nine species. The Lance Creek and the Hell Creek beds furnish three or 

 four species of the family, most of which are referred to the genus Hadro- 

 saurus, or Trachodon. Whether or not there are species common to the 

 two formations cannot now be definitely determined; but certainly their 

 relationships are A T ery close. 



Of all the dinosaurs that are found in the formations in which our 

 interest is now centered the Ceratopsia have received the most careful 

 study. What the present state of knowledge is with regard to these re- 

 markable reptiles, may be learned from Hatcher's monograph of the 

 group, completed and edited by Dr. Lull (Mon. 49. U. S. Geol. Surv. ). 

 Unfortunately much needs yet to be learned about them, especially about 

 those of the Judith River forms. Approximately nine species are known 

 from the Judith River deposits of Montana and British America ; and 

 about fifteen species are credited to the Lance Creek beds, of Wyoming, 

 and to the Arapahoe and the Denver, of Colorado. Hatcher and Lull con- 

 clude that those of the Judith epoch are somewhat more primitive than 

 those of the beds higher up. being somewhat smaller, with a less completely 

 developed nuchal frill, with the nasal horn relatively larger and the 

 supraorbital herns relatively smaller than in the younger forms. It is, 

 however, to be noted that the nasal horn of Ceratops, of the Judith River 

 epoch, is not yet certainly known. For the most part the genera are 

 based on the characters mentioned above. They may have the importance 

 assigned to them, but they do not indicate radical differences. Such differ- 

 ences might easily have arisen during an interval of moderate duration. 

 There can be no doubt that the Ceratopsia of the higher beds were derived 

 directly from those of the lower. 



The possibility may be fully granted that further investigations may 

 prove that few or no species of vertebrates continued from the Judith 



