Cope.] b % £i£i [Jan, 18, 



Day and Ticholeptus Miocene horizons. The M. rusticus of Leidy is only 

 known to me from the descriptions of that author. It is from the Sweet- 

 water river, Wyoming, from a bed of probably Ticholeptus age. The 

 M. proprius Leidy, also unknown to me by autopsy, is from the head ot 

 the Niobrara river, Nebraska, from a bed said by Hayden to be inter- 

 mediate between the Oreodon or White River and Procamelus, or Loup 

 Fork horizons, and therefore probably ot Ticholeptus age also. The M. 

 leidyi I only know from the description of Mr. Bettany. It is from the 

 John Day beds. Mr. Bettany also describes an M. temporalis, w r hich I 

 cannot distinguish from the M. superbus Leidy. 



Merycochcerus superbus Leidy. 



Oreodon superbus Leidy, Proceedings Academy Philadelphia, 1870, p. 

 109. Extinct Mam. fauna, Dakota and Nebraska, 1869, p. 211 ; Plate I, 

 fig. 1 ; II, fig. 16 ; VII, figs. 7-11. M. temporalis Bettany, Quar. Journ. 

 Geol. Soc, London, 1876, xxii, p. 269 ; PI. XVII. 



Of this fine species I have nine crania extracted from the matrix, and 

 a good many not yet cleaned. As the specimen described by Leidy is in 

 a very imperfect condition, the characters of the species, and even its 

 generic position, have remained hitherto very obscure. 



As compared with the allied species, the M. superbus is slightly exceeded 

 in size by the M. macrostegus and M. montanus. Its posterior zygo- 

 matic expansion is less pronounced than in the M. macrostegus and M. 

 chelydra, and its border is rounded, even when, as is sometimes the case, 

 it is greatly thickened. In the first and last named of the above species, 

 its border is separated by a distinct angle from both the internal and ex- 

 ternal faces, forming thus a distinct truncate face which looks upwards. 

 The otic bulla is larger than in the two species mentioned, and extends 

 anterior to the postglenoid process. The nareal fissure extends well down 

 towards the alveolar border of the premaxillaries, which are therefore 

 more extensively separated than Leidy represents to be the ca.se in the M. 

 rusticus. The external face of the malar bone below the orbits is flat. 

 The anterior extremity of the zygomatic process is not so prominent as in 

 M. chelydra, and is rounded instead of being flared out below, as in that 

 species. The greatest width of the skull is at the glenoid surfaces, and 

 not anterior to them, as in M. chelydra. In only one of seven crania, 

 where the parts are preserved, does the posterior squamosal angle rise as 

 high as the sagittal crest. 



I cannot detect any difference between the specimen described by Mr. 

 Bettany as the type of his M. temporalis, and those of the M. superbus 

 in my possession. The shallowness of the preorbital fossa described by 

 Mi". Bettany is repeated in one of my crania, and its depth is very vari- 

 able in the others. As regards the M. leidyi of Bettany, I have none ex- 

 actly like it, although the type specimen does not differ much from the 

 M. superbus, to judge from the figure and description given in the Quarter- 

 ly Journal of the Geological Society, 1876, p. 270. The two distinctive 



