South Dakota School of Mines 111 



of the material is made up of skulls and detached bones. Few 

 complete skeletons have been obtained and until recent years 

 little attempt was made at restoration. The dentition is remark- 

 ably complete the total number of permanent teeth being forty- 

 four arranged in nearly unbroken series in both jaws. The 

 formula for each side above and below is as follows : Incisors 

 three; canines, one; premolars, four; molars, three. Total forty- 

 four. Of the Oreodons Oreodon culbertsoni is by far the most 

 common. Leidy says that of the five hundred he had observed 

 about four hundred and fifty were of this species. Oreodon 

 gracilis, about two-thirds as large as Oreodon culbertsoni, was 

 perhaps the next in abundance. Its skull was about the size 

 of the red fox and a skeleton mounted by Mr. C. W. Gilmore 

 of the U. S. National Museum measured twenty seven inches 

 in length and is twelve and one-half inches high at the 

 shoulders. Mporeodon major, earlier called Oreodon major, is 

 still rarer. It is about one-fifth larger than Oreodon culbertsoni 

 or nearly twice as large as Oreodon gracilis. 



The literature on the Oreodontidae is widely scattered 

 through the various scientific periodicals and special publications. 

 Many of the papers listed in the Bibliography near the close of 

 this publication, contain descriptions of species. So far as I am 

 informed there has been no recent exhaustive resume of the 

 subject. Prof. Cope, many years ago, 1884, published in the 

 Proceedings of the American Philosophical Society, Vol. 21, pp. 

 503-572, a synopsis of the species of Oreodontidae. Later, 

 1890, Prof. Scott published an important contribution to the 

 knowledge of the subject,* but I have not had recent oppor- 

 tunity to examine this paper. Brief summary descriptions of 

 more recent date may be found in several of the better ency- 

 clopedias and text books of paleontology. 



HYPERTRAGUUDAE 



The Hypertragulidae include some of the most interesting 

 fossil mammals ever discovered. They are ancient selenodonts 

 (ruminants) resembling in a way the little chevrotain or "deer- 

 let" of India and the musk deer of the Asiatic highlands but 

 they are in reality not closely related to either. They seem to 

 represent an independent offshoot of the primitive ruminant 

 stock but near relatives, either ancestral or descendent are not 

 known. 



*Scott, W. B. Beitrage zur Kenntniss der Oreodontidae. Morpho- 

 log. Jahrbuch, Vol. 16, pp. 319-395, pis. XII-XVI, 10 fgs. 



