DAKOTA AND NEBRASKA. 165 



contains portions of lower jaAvs and teeth of ifer?/corZMS «eca/MS, obtained on Little 

 Wliite Eiver, or the Soutli Fork of the main stream. A jaw fragment agrees in 

 chai-acter with the Niobrara River specimens, except that it is rather more robust in 

 its proportions, the difference being apparently due to difference in age. Its measure- 

 ments, in comparison with the Niobrara specimens, are as follow : 



Specimens from L. "White R. Niobrara E. 



Lines. Lines. Lines. 



Depth of jaw at first premolar, . 



Depth at middle of first true molar. 



Depth at middle of last true molar, 



Depth one-third of an inch in advance of the molars, 



Space occupied by six molars, . 



Sj)ace occupied by true molars, . 



SjDace occupied by last two premolars, . 



Breadth of second true molar, - 



Breadth of last true molai', above, 



MOSCHID^. 



6i 6 



7i 7 7i 



10 8 



4* 4 



25 25 



16 16 15 



6 6 



51 5 4J 



7 7 



This family is represented in the Mauvaises Terres miocene formation by the 

 remains of an extinct genus, to which I have given the name of Leptomeryx. Its 

 remains were obtained from beds B and D of Dr. Hayden's section. 



LEPTOMERYX. 



The genus distinguished by the above name is founded upon the fossil remains of 

 a small ruminant, allied to the recent Musks, discovered in association with remains 

 of Oreodon Culbertsoni, 0. gracilis, Ancliitlierium Bairdii, &c., in the miocene tei'tiary 

 deposits of Dakota. The skull of Lepiomeryx has the general conformation of that of 

 the Musks, is unprovided with antlers, and has no ant^orbital lachrymal fossee. The 

 jaws are provided with continuous rows of six molars on both sides, as in most recent 

 ruminants. 



Leptomeryx Evansi. 



The species and genus above named was first characterized by a specimen, consist- 

 ing of a mutilated skull, accompanied with a portion of the lower jaw, discovered by 

 Dr. John Evans in the Mauvaises Terres of White River, Dakota. Subsequently 

 Dr. Hayden obtained portions of several less well-preserved skulls, together with a 

 multitude of fragments of jaws with teeth, and some portions of other bones of the 

 skeleton, partly from the same region, and partly from Bear Creek, a tributary of the 



