182 THE MAMMALIA OF THE DEEP RIVER BEDS. 



Mesoreodon ; its resemblances to Merycochosrus are due to parallelism and not to 

 relationship. Hence it is impossible to unite these two genera, as has been proposed. 



(13) Leptauchenia is a White River genus, and the difficulty caused by suppos- 

 ing the three genera of this line to be contemporaneous thus disappears. 



(14) A second and somewhat smaller species of Blastomeryx is described from 

 the upper beds, and considerable portions of the skeleton show that this species was 

 in size and general appearance very similar to the prong-horn antelope, though with 

 many cervine features. The genus is shown to be closely allied to the European 

 PalcBomeryx and was doubtless derivedfrom the Old World, nothing being known 

 in the John Day or White River beds from which it could be descended. The pecu- 

 liarities of the horns and the occipital region are such as to render it doubtful 

 whether this genus can be ancestral to any existing form. At most, it may be so 

 related to Antihcapra. 



(15) The axis of Protoldbis has an odontoid process which may be described as 

 in the incipient stage of the spout-shape and corresponding to that of Miohippus 

 among the horses. The evolution of this structure proceeded by exactly- similar 

 steps in the horses and camels and is to be correlated with the increasing length of 

 the neck and the increased angle included between the axes of the cranium and of 

 the cervical vertebrae. 



List op Papers Quoted. 



1. Bettant, G. T. : On the Genus Merycochmrus, etc. Quarterly Journal of the Geological Society of London, 



Vol. XXXII. 



2. Branco, W. : Ueber eine fossile Saugethier-Fauna von Punin bei Riobamba in Ecuador. Palreontologische 



Abhandlungen von Dames und Kayser, Bd. I. 



3. Cope, E. D.: The Relations of the Horizons of Extinct Vertebrata of Europe and North America. Bulletin 



U. S. Geolog. and Geograph. Survey of the Territories, Vol. V, 1879. 



4. On the Canida of the Loup Fork Epoch. Ibid., Vol. VI. 



5. Extinct American Rhinoceroses and their Allies. American Naturalist, Vol. XIII. 



6. The Mesozoic and Cenozoic Realms of the Interior of North America. Ibid., Vol. XXI. 



7. The Artiodactyla. Ibid., Vols. XXII and XXIII. 



8. The Vertebrate Fauna of the Ticholeptus Beds. Ibid., Vol. XX. 



9. Tertiary Vertebrata. Rep't U. S. Geolog. and Geogr. Survey of the Territories, Vol. III. 



10. Synopsis of the Species of Oreodontidte. Proc. Arner. Philos. Soc, Vol. XXI. 



11. Preliminary Report on the Vertebrate Palaeontology of the Llano Estacado. Geological Survey of Texas, 



4th Ann. Report. 



12. Dall, W. H., and Harris, G. D. : The Neocene of North America. Bulletin of the V. S. Geological Survey, 



No. 84, 1892. 



