M. R. Thorpe — A New Merycoidodon. 341 



Synopsis of Species. 



1. Posterior part of nasal bones acute. 



Infra-orbital foramen above interval between P^ and P^; 

 frontals produced considerably forward of lacrymal 

 bone ; orbits nearly circular ; short sagittal crest ; length 

 190-210 mm M. culhertsonii culhertsonii 



Infra-orbital foramen above extreme posterior part of P^ ; 

 frontals produced a little forward of lacrymal bone; 

 short sagittal crest ; length, 150-160 mm. 



M. culhertsonii pericidorum 



Infra-orbital foramen above posterior part of P^ ; same as 

 M. culhertsonii culhertsonii in general, except much 

 more robust and face one-third higher above P^ ; length, 

 192 mm M. macrorJiinu^ 



2. Posterior part of nasal bones obtuse. 



Infra-orbital foramen above interval between P^ and P^ ; 

 frontals produced only slightly forward of lacrymal 

 bone ; short sagittal crest ; length, 123-133 mm. 



M. gracilis 



Infra-orbital foramen above middle of P^; frontals pro- 

 duced slightly farther forward of lacrymal bone than in 

 above; long sagittal crest; much greater breadth at 

 posterior margin of orbits than in M. gracilis; length, 

 136 mm M. affinis 



Infra-orbital foramen above interval between P^ and P*; 

 frontal and lacrymal bones coextensive forward; long 

 sagittal crest ; length, 155 mm. .ilf . platycephalus, sp. nov. 



Eeferences. 



Cope, E. D. : 1884. Synopsis of the species of Oreodohtidse. Proe. Amer. 

 Philos. Soc, 21, 503-572. 



— 1888. The Artiodactyla. Amer. Nat., 22, 1079-1095. 



Douglass, E. : 1902. Fossil Mammalia of the "White Eiver beds of Montana. 

 Trans. Amer. Philos. Soc, 2d ser., 20, 264-265. 



— 1903. New vertebrates from the Montana Tertiary. Ann. Carnegie Mus., 



2, 163. 



Gilmore, C. W. : 1906. Notes on a newly mounted skeleton of Merycoido- 

 don, a fossil mammal. Proe. XJ. S. Nat. Mus., 31, 513-514. 



Hay, O. P. : 1902. Bibliography and catalogue of the fossil Vertebrata of 

 North America. U. S. Geol. Survey, Bull. 179. 



Leidy, Joseph : 1848. On a new fossil genus and species of ruminantoid 

 Pachydermata : Merycoidodon culhertsonii. Proe. Acad. Nat. Sci., 

 Philadelphia, 4, 47-50. 



— 1851. A. Descriptions of fossil ruminant ungulates from Nebraska. 



Ibid., 5, 276. 



— 1851. B. (Remarks on Oreodon priscus and BJiinoceros occidentalis.) 



Ibid., 5, 276. 



— 1869. The extinct mammalian fauna of Dakota and Nebraska, etc. 



Jour. Acad. Nat. Sci. Philadelphia (2), 7, 1-472. 



Am. Jour. Sci.— Fifth Series, Vol. II, No. 12. — December, 1921. 

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