344 Jti. S. Lull — Mammals and Horned Dinosaurs. 



if not identical T. brevicornus, probably T. serratus and 

 T. horridus. All are of moderate size with the exception of 

 the last and their range in the stratigraphic column is low, 

 especially as Skull 22 and possibly 21 in the table may be 

 placed entirely too high. 



Of the second Triceratojps phylum T. elatus is typical. In 

 this race the nasal horn is very small and set well back from 

 the terminus of the beak ; the brow-horns, on the contrary, are 

 very large. To this group belong T. calicornis, closely related 

 to if not identical with T. elatus ; probably also the immature 

 though large T. flabellatus, and the gigantic "Skull 24" to 

 which Marsh gave the manuscript name of Triceratojps ingens. 



The members of this second phylum are all large and range 

 through the middle and upper portion of the Lance. To derive 

 them from the first phylum would necessitate the retrogression 

 of the nasal horn to which certain critics (Gidley in Peale, 

 1912, p. 751) object, although the principle is certainly well 

 established in evolution. I am willing, however, to accept 

 Mr. Gidley's main contention of the improbability of the 

 reduction of a highly developed nasal horn while the brow- 

 horns were being developed to be the principal ones. 



Mammalian Localities 



The table of ceratopsian distribution also shows the nearest 

 mammal localities stratigraphically to each skull, and has 

 enabled me to arrange them in an approximate sequence 

 which, however, is open to the same chance for error as that 

 of the skulls in that it is derived largely from the study of the 

 map and the sections. It should, therefore, be verified by 

 further accurate field work. 



One thing at least is certain, that instead of being confined 

 to any one level, mammalian remains are found throughout 

 nearly the entire Ceratopsia-bearing beds. 



From Peterson's quarry, Beecher's quarry, and Quarries Nos. 

 1-10 we have a recorded mammalian fauua. From Quarries 

 11-27 there is no recorded material at Yale or at Washington, 

 so that at present I am unable to give a list of genera and 

 species from them. This is unfortunate, as the four quarries 

 highest in the list are included within the number and a record 

 of their mammalian contents would be of great interest. 



There are also a number of species of which the types bear 

 no quarry number but which are in part duplicated by 

 unnamed material the source of which is indicated. 



The following table gives Marsh's original genera and species 

 and in the adjacent columns their distribution in the several 

 quarries is indicated. I have also identified in so far as 

 possible all the additional material from these quarries, with 



