Xri. THE OSTEOLOGY OE PROMERYCOCIKERUS. 

 By O. a. Peterson. 



(Plates XXXIII-XLII). 



The fine material representing the genus Promerycochcerus Douglass, 

 which was collected by the expeditions of the Carnegie Museum in 

 1901-1902 in the Miocene deposits of Nebraska and eastern Wyom- 

 ing, having been prepared for study, the writer was encouraged by 

 Dr. W. J. Holland, the Director of the Museum, to undertake its 

 description and the following pages represent the results. 



In common with my scientific associates in the Museum I wish to 

 express the gratitude which we feel towards Mr. Andrew Carnegie, 

 whose munificence made possible our journeys of research, and the 

 consequent discoveries. I take the present opportunity to thank 

 Dr. Holland not only for the unrestricted use he allowed me to make 

 of the very remarkable skeletal remains with which this paper deals, 

 but also for his revision of the manuscript and his kind suggestions 

 and criticisms. I wish especially to recognize the assistance he gave 

 Mr. Theodore A. Mills in preparing the models, figures of which are 

 herewith published on Plates XXXVI and XXXVII. Thanks are 

 due to the authorities of the American Museum of Natural History in 

 New York for permission to publish herewith the illustrations of 

 Promerycochcerus chelydra Cope. I also desire to express my appreci- 

 ation of the skill and patience shown by Mr. Sidney Prentice in making 

 the drawings for this paper, and of Mr. A. S. Coggeshall in making 

 the photograjihs. 



Genus Promerycocho-.rus Douglass. 



Earl Douglass, American Journal of Science, Vol. XI, 1901, p. 82. — W. D. 

 Matthew, Memoirs American Museum of Natural History, Vol. I, 1901, p. 398. — 

 O. A. Peterson, Annals Carnegie Museum, Vol. IV, 1907. PP- 26, 36. — Earl 

 Douglass, Annals Carnegie Museum, Vol. IV, 1907, pp. 84-109. 



The genus Promerycochcerus was first proposed by Earl Douglass 

 {P. superbus being designated as the type /. c, p. 82). Later Dr. \V. D. 

 Matthew accepted the genus as \a\{(\ and lengthened Douglass' 



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