106 



ON THE EXTINCT MAMMALIA OF 



Oeeodon. 



Breadth at post-orbital arches, 



Breadth at ant-orbital margins, 



Breadth at infra-orbital foramina, . 



Breadth above last molars, .... 



Breadth of hard palate between first true molars, 

 Breadth of nasals above infra-orbital foramina, 

 Breadth of nasals at ends of frontal processes, . 

 Length of nasals back of " " . 



Height of orbits, ...... 



Distance between supra-orbital foramina, 

 Length of upper true molar series, . 



Measurements in lines. 



36 



28 



15* 



28 



lU 



9 

 lOJ 



8 

 11 



6} 

 18 



HYBRIDUS GRACILIS. CdLBEBT'i 



48 



36 

 22 

 38 

 17 

 lOi 

 11 

 10 

 16 

 8J 

 22 



26 

 21 

 1-2 

 21 

 9 



7 



9 



5 



15 



36 



27 



17 



30 



15 

 Ik 

 7* 



10} 



15 

 4 



22 



48 

 ;-i8 

 21 

 40 

 18 

 14J 

 14 

 18 

 15 

 7 

 26 



Oreodon bullatus. 



The collection of fossils obtained in the Mauvaises Terres, in Dr. Hayden's expedi- 

 tion of the summer of 1866, has afforded me the opportunity of examining a multi- 

 tude of additional specimens of skulls and fragments of others, with teeth, of Oreodon 

 Culhertsoni. Besides those which present the ordinary individual variations, there is 

 one specimen which exhibits a most remarkable and unexpected deviation of charac- 

 ter. The specimen consists of a mature skull, much fractured, and having one side of 

 the face broken away. The other side retains the molars, with part of the corres- 

 ponding canine tooth. 



The skull agrees in general form, size and details of structure with that ordinarily 

 of Oreodon Culhertsoni, except that it possesses inflated auditory buUas proportionately 

 as large and nearly of the form of those of Oreodon major. In 0. Culhertsoni the 

 auditory bullte are proportionately less well developed than in 0. gracilis, so that I 

 was totally unprepared to see a skull, which otherwise would have been referred with- 

 out hesitation to 0. Culhertsoni, with bullae approaching in size those of 0. major. 

 Had the cranium alone of this singular specimen been found, it would have been 

 viewed as pertaining to AgriocJioerus, because in its form, size, construction, and 

 possession of large inflated auditory bullce, it agrees with that of the latter genus, but 

 then it has the face and teeth of Oreodon Culhertsoni. The discovery of this specimen 

 throws doubt on a previous determination of some isolated crania which were referred 

 to AgriocTioerus, and in part at an earlier period, or before an entire skull of the 

 latter had been obtained, to a supposed distinct genus named Eucrotaphus. 



Measurements of the above skull are given, in comparison with those of 0. Cid- 

 berisoni, as specimen number 18, page 92. 



Of other portions of the Skeleton of Oreodon. 



The various collections of fossils from the Mauvaises Terres which I have had the 

 opportunity of examining, contain a great multitude of fragments of the skeleton of 



