PROCEEDINGS OF THE UNITED STATES NATIONAL MUSEUM 



issued 



SMITHSONIAN INSTITUTION 



U. S. NATIONAL MUSEUM 



Vol. 87 



Wa.hington: 1939 No. 3066 



CERATOPSIAN DINOSAURS FROM THE TWO MEDICINE 

 FORMATION, UPPER CRETACEOUS OF MONTANA 



By Charles W. Gilmore 



Three expeditions for dinosaurian remains have now been con- 

 ducted by me to the Two Medicine formation, as exposed on the 

 Blackfeet Indian Reservation in northern Montana. These explora- 

 tions have resulted in the accumulation of a considerable number of 

 dinosaurian specimens, among which are several pertaining to the 

 Ceratopsia that are of more than ordinary interest. 



The first expedition, in 1913, under the auspices of the U. S. 

 Geological Survey, discovered the type and other materials of 

 Brach^ceratops montanensis,^ all juvenile specimens; the second, in 

 1928, recovered the type of Styracosaurus ovatus^ and portions of 

 the skull and skeleton of a Monodonius flexus; and the third, in 1935, 

 yielded two fragmentary skeletons pertaining to the genus Lepto- 

 ceratops and a disarticulated skull and a few bones of a nearly adult 

 Brachyceratops montanensis. These specimens of the 1935 expedition 

 are described in the present paper. The figures illustrating them 

 were drawn by Sydney Prentice. 



Family PROTOCERATOPSIDAE 

 Genus LEPTOCERATOPS Brown 



LEPTOCERATOPS species 



The two specimens of Leptoceratops found in the Two Medicine 

 formation for the most part are very fragmentary, but sufficiently 



1 Gilmore, C. W., Smithsonian Misc. Coll., vol. 63, No. 3, pp. 1-10, 1914. 



2 Gilmore, C. W., Proc. U. S. Nat. Mus., vol. 77, art. 16, pp. 36, 37, pi. 10, figs. 1, 2, 1930. 



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