248 E. L. Troxell — Entelodonts in Marsh Collection. 



in the early days of his paleontological work; but more 

 especially, by detailed descriptions and drawings, to lay 

 more broadly the foundation on which to study these ani- 

 mals in the future. The fine drawings are due to the 

 artistic skill of Mr. R. Weber. 



It is especially fitting, at the beginning of my work 

 here as a member of the Peabody Museum staff, to ex- 

 press my gratitude to the two men, Professor Schuchert 

 and Professor Lull, my former instructors, who have been 

 most generous in their sympathy and assistance, and who 

 now offer me every advantage in carrying on the work of 

 my choice. To my congenial associates and myself the 

 whole Marsh collection is thrown open for study and de- 

 scription under circumstances most propitious. 



With reference to the group of entelodonts in particu- 

 lar, some of the Marsh specimens are entirely new, some 

 of them had never been carefully studied before, and most 

 of the material had never been completely prepared. In 

 several instances, well known specimens have been further 

 developed so that now new features are observed, giving 

 evidence which contradicts some of the conclusions of for- 

 mer studies. The present paper treats almost exclu- 

 sively the fossils in the Marsh Collection of the Peabody 

 Museum at Yale. 



In earlier paleontological writings, types were made on 

 single molars or on a fragment of bone without teeth. In 

 attempting to use these fragmentary types as guides, it 

 becomes very evident that we cannot depend upon the 

 characters shown by a single tooth or other small part of 

 the fossil; we must know a large part of the skull; we 

 should know the whole skeleton. 



Status of species. — There were some twelve or fourteen 

 species referred from time to time to Entelodon (Elother- 

 ium, see Peterson 1909, p. 43) and finally to the true 

 American forms Archceotherium, Pelonax, Ammo don, 

 Dinohyus, etc. ; of these, recent authors recognize but few. 

 Following is a list of the Oligocene forms commonly seen 

 in the literature : 



Entelodon magnus Aymard 1846. E. coarctatus Cope 

 1889. E. calkinsi (Sinclair) 1905. Archceotherium mor- 

 toni Leidy 1850. A. robustum Leidy 1852. A. ingens 

 (Leidy) 1856. A. superbum (Leidy) 1868. A. imperator 

 (Leidy) 1873. A. crassum (Marsh) 1873. A. clavus 

 (Marsh) 1884. Pelonax ramosus Cope 1874. P. potens 



