HISTORY OF DISCOVERY 5 



Charles W. Gilmore of the United States National Museum explored for horned dinosaurs 

 especially in the Blackfeet Indian Reservation in northwestern Montana in 191.1. Here, exposures 

 of the Two Medicine formation were found along the Milk River near the Canadian boundary. The 

 collection was small, but of great interest since it contained several specimens of the only adolescent 

 ceratopsian found in America, the type of Brachyceratops (PI. IX, B), as well as other recognizable 

 material. He also collected here the type of Styracosaurus ovatus. 



The discovery of Pro toe era tops in Mongolia by the American Museum expedition of 1922 under 

 Andrews and Granger has opened a new chapter in ceratopsian history, for it gives not only the first 

 record of the group outside the limits of North America, but also for the first time an ontogenetic 

 record of a ceratopsian genus. The collection includes eggs and all stages of growth from the newly 

 hatched young to the old adults. Several skeletons and no fewer than 73 skulls were included in 

 the finds. 



The principal desideratum from the standpoint of ceratopsian study would be further explora- 

 tion in the Judith River formation of northern Montana for the purpose of securing additional mate- 

 rial to clarify our conception of the early Cope and Marsh genera, Monoclonius and Cera/ops, of 

 which our knowledge is so very imperfect owing to the fragmentary condition of the types. Another 

 region deserving more exploration is New Mexico, which is sure to yield ceratopsians other than 

 Pentaceratops, a genus which, with one authentic and another doubtful species, represents all that we 

 know of the southern horned dinosaurs. 



