1884.] -•-' [Cope. 



of a superior maxillary bone which contains the M. i and the alveolus of 

 the P-m. iv, with the foramen infraorbitale anterius. The measurements 

 of the M. i agree with those of the corresponding tooth of the lower jaw of 

 Leidy's specimen. In the Museum of Mexico, there are preserved several 

 superior true molars which also agree in dimensions with the correspond- 

 ing teeth of the lower series of the type of the same A. hesterna of Leidy. 

 The fourth superior premolar is wanting from this series. 



The fragment of maxillary bone in the Condon collection shows that 

 this species had a large three-rooted fourth premolar. It is broken off at 

 the anterior alveolus, but it is so attenuated at that point as to make it 

 almost certain that there was no third premolar in front of it, as is found 

 in the genus Auchenia. 



In further evidence of the existence of a genus characterized as above, 

 by the absence of the P-m. ^, the jaw-fragment which represents the 

 Auchenia vitakeriana* may now be cited. 



Holomeniseus mtakerianus Cope. 



Although I ascribed a third superior premolar to this species, I must 

 now deny its existence in the adult animal. A slight fossa on the narrow 

 alveolar ridge indicates the possible presence of a single-rooted rudiment 

 of such a tooth in the young. In a comparison of this species with the 

 Auchenia weddeUii Gervais, from the Pampean beds of Buenos Ayres, it 

 is readily observable that the latter is a true Auchenia, with well devel- 

 oped P-m. 3 in the upper jaw, and that it is of larger and more robust pro- 

 portions than the E. vitakeriana. In the only well preserved lower jaw 

 which I possess, there is a well developed P-m. iii, a tooth found only as 

 an occasional accident in Auchenia lama (teste Owen Odontography). In 

 the A. intermedia Gerv., from the same locality, this tooth is wanting 

 from one ramus, while the other displays a shallow vacuity as though 

 such a tooth had existed in infancy and had been shed. I therefore retain 

 these species in Auchenia. 



HoLOMENiscus HESTERNUs Lcidy. Aucheuia hesterna Leidy, loc. sup. 

 cit. 



The existence of superior molars in the Museum Nacional of Mexico 



which agree with the corresponding teeth of the Califoruian and ( )regonian 



llamas has been mentioned above. I give the dimensions of these teeth as 



follows : 



Measurements. M . 



f anteroposterior 041 



DiamctersM. i^ransverse 033 



^ ^anteroposterior 041 



Diameters M. ii i ,hransverse 040 



)■ one mdividual. , . ,_., 



Diameter M. iii [ '■ anteroposterior Ooo 



j *- transverse 029 



* Bulletin of the U. S. Geological Survey Terrs., 1878, p. 380. 

 PROC. AMER. PHILOS. SOC. XXII. 117. C. PRINTED OCTOBER 22, 1884. 



