MERYCOIDES 171 



Description: This tooth resembles the comparable one in P. siouense, both in crown pattern 

 and in size. It has a weak anterior crescent, and the anterior part is somewhat less prolonged than 

 is normal for the genus. The median crest is well developed, and there are no intermediate crests. 

 I believe that the tooth represents the genus Pronomotherium in Oregon and that it is nearest to 

 P. siouense, and yet I hesitate to place it in that species, basing the evidence upon but a single tooth. 



TICHOLEPTUS-METOREODON STOCK 



Genus MERYCOIDES Douglass 1907 

 Table 1 



Original Reference: Some new merycoidodonts. Ann. Carnegie Mus., IV, pp. 101-102, pi. 24. 



Genotype: Merycoides cursor Douglass. 



Genoholotvpe: Cat. No. 1222 CM., skull, jaws, and part of skeleton. 



Distinguishing Characters: Skull moderately large and mesocephalic, tending toward 

 dolichocephaly; nasals, as well as premaxillaries, somewhat reduced; face, including orbits, more 

 than half the total length of skull; lacrimal fossx deep; facial vacuities present in M. longiceps 

 only; frontals unreduced; zygomatic arches slender and malar medium; brain case low and wide 

 to elongate; bulla; large; mandible rather slender; dentition brachyodont to subhypsodont ; teeth 

 44; limbs and feet moderately slender. 



Discussion: Loomis, in 1924, grouped Merycoides, Phenacoccelus, and Metoreodon around 

 the Ticholeptus stem. To this I should add Paroreodon, and I believe that Poatrephes belongs here 

 too. Most of these forms have facial vacuities, deep pits on either side of the occipital pillar, rela- 

 tively light zygomatic arches, and medium type of limbs. 



The dentition Loomis (1924B, p. 12) describes as follows, as being distinctive of the Ticho- 

 leptus group: 



In all these genera the anterior portion of the upper premolars is shortened, the median crest is weak, and the 

 posterior crescent, though swollen, does not unite with the median crest. In the lower premolars the anterior 

 intermediate crest and the anterior crescent are lacking or weak. The posterior portion of premolar 3 is always 

 inclosed by the median crest, posterior crescent and posterior crest, and into this basin the posterior intermediate 

 crest projects from the rear. Premolar 4 has the rear portion of the tooth inclosed like that of premolar 3, but 

 there is no posterior intermediate crest. There is a marked tendency for the pillar-like cusp to be developed and 

 to project far forward into the anterior basin. 



Etymology: Merycoides (ruminant + like). 

 Species: 



M. cursor Douglass 1907. Genotype. 



M. latidens (Douglass) 1907. 



M. longiceps (Douglass) 1907. 



Merycoides cursor Douglass 1907 

 Fig. 124; PI. XXV 



Original Reference: Some new merycoidodonts. Ann. Carnegie Mus., IV, pp. 101-102, pi. 24. 



Type Locality: Canon Ferry, on Missouri River, east of Helena, Montana. 



Geologic Horizon: Lower Miocene (lower Harrison). 



Type: Genoholotype, Cat. No. 1222 CM., skull and jaws nearly complete, inferior part of scapula, part of 

 humerus, superior end of radius, proximal and distal ends of femur, parts of two tibiae, a tarsus, third and fourth 

 metatarsals (lacking distal ends), and a rib which had been fractured and had healed during the individual's 

 lifetime. Collected by Earl Douglass in 1902. 



