GEOLOGIC DISTRIBUTION 



(Fig. 1) 



The known Ceratopsoidea, both of North America and of Asia, are confined to the Upper 

 Cretaceous (Senonian and Danian of European usage), and thus far have been found in non-marine 

 strata only. In North America, they extend through several horizons, from the Belly River where 

 they appear abruptly, to the very close of the Lance formation where, with equal abruptness, they 

 disappear. 



I am indebted to Doctors L. S. Russell 1 of the Geological Survey of Canada and T. W. 

 Stanton 1 of the United States Geological Survey for information concerning the correlation of 

 United States and Canadian horizons. The statements derived independently from these two high 

 authorities entirely agree, and from the tables of correlation that they furnished, the combined one 

 here published (Fig. 1 ) has been made. 



In Alberta, two principal horizons have produced Ceratopsia. The first is the Belly River, in 

 which the fossils are restricted to the Pale or uppermost beds of the series. Then, after an interval 

 represented by the marine Bearpaw formation, these animals reappear in the Edmonton, above which 

 there is no record of their occurrence in Alberta. 



In Glacier County, Montana, the Ceratopsia-bearing horizon is the Two Medicine, the equiva- 

 lent of the Belly River series of Alberta; but here again these dinosaurs, of which only a very 

 few have been found, are known from the upper part alone. In central Montana, the Judith River, 

 equivalent again to the upper half of the Two Medicine and to the Pale and Foremost beds of the 

 Belly River series, has produced ceratopsians whose closest equivalents taxonomically seem to lie 

 among those of the Belly River, although with curious morphological differences which will be 

 discussed, p. 27. Ceratopsia from the Judith River are ill known, due largely to pioneer collect- 

 ing, nor is their precise stratigraphic position within the formation clear. They do not seem to be 

 limited to any part of the horizon as in the Belly River series, according to available evidence. 

 Above the Judith River comes a longer interval of marine deposition than in Alberta, for the non- 

 marine Lance (Hell Creek beds) is separated from the Judith River by both the Bearpaw and the 

 Fox Hills formation, hence such annectant genera as those found in the Edmonton are entirely 

 absent. 



Niobrara County, Wyoming, contains the classic Lance locality, the so-called "Ceratops beds" 

 of Marsh, out of which have come almost all of the principal types of the latest of the ceratopsians, 

 Triceratops, Diceratops, and Torosaurus. The last genus, so far as we know, is found nowhere else. 



In the Denver Basin of Colorado, the formations equivalent in time to the earlier Ceratopsia- 

 bearing horizons are all marine, and hence it is only in the uppermost Cretaceous, in the Denver 

 and Arapahoe beds, correlated with the Lance, that a few horned dinosaurs have been found, which 

 are the generic equivalents of those of Wyoming and Montana. 



A new locality, the Ceratopsia of which were unknown at the time of the publication of the 

 Ceratopsia Monograph, lies in San Juan County, New Mexico. Here the non-marine formations 

 are late in Cretaceous time and, as our table shows, are homotaxial with the Edmonton of Alberta 

 and with the Lance of Montana and Wyoming. Of these, the Fruitland and Kirtland, equivalent 

 to the Edmonton, have been the most productive, revealing a genus, Pentaceratops, which is mor- 

 phologically older than Triceratops or Torosaurus but younger than the Belly River ceratopsians. 

 Some material is also recorded as possibly from the Ojo Alamo; but one cannot be sure either of 

 the generic identity or of the stratigraphic reference, for the term Ojo Alamo 2 is said to have been 



1 Letters to the author, 1933. 



2 Brown, B., 1910. 



