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THE Vj^y^S^ 



AMERICANJOURNALOFSCIENCE 



[FOURTH SERIES.] 



Akt. XXYI. — The Mammals and Horned Dinosaurs of 

 the Lance Formation of Niobrara County, ~Wyoming; by 

 Richard Swann Lull. 



[Contributions from the James Dwight Dana Memorial Fund, Yale University.] 



Introduction 



The problem 



Historical resume 



Descriptions by Professor Marsh 



Summary of the Lance fauna 



Comparison with the Belly River fauna 



Comparison with the Paskapoo fauna 



Comparison with the Fort Union fauna 



Summary 

 Eeconnaissance of 1914 

 Stratigraphy of the Lance formation 



Beecher's section, 1889 



Hatcher's section, 1893 



Stanton and Knowlton's sections (a, 6), 1897 and 1909 



Stanton's section (c), 1909 



Doneghy's section, 1914 

 Ceratopsian localities 



Geologic sequence 



Evolutionary sequence 

 Mammalian localities 

 Summary 

 Bibliography 



Introduction 



Ever since the completion of the Ceratopsia monograph in 

 1905, the writer has desired to visit the famous region which 

 produced so many of the remarkable creatures which form the 

 subject-matter of that volume. Last summer, through the 

 kind cooperation of my colleague, Professor Schuehert, an ex- 

 pedition to Nebraska was made possible, and when a visit to 

 the " Ceratops beds " of Wyoming was also planned, Mr. 

 Schuehert immediately suggested that a • reconnaissance be 

 made with the particular purpose of determining, if possible, 



Am. Jour. Sci. — Fourth Series, Vol. XL, No. 238. — October, 1915. 

 21 



