42 



THE MERYCOIDODONTID/E 



Discussion: This species resembles Oreonetes in that there is no trace of a protoconule on the 

 superior molars, but P 4 is different in its anteroexternal construction. The species is seemingly 

 much closer to the Limnenetes line in the construction of P 4 and of the upper molars, as well as in 

 the lower dentition so far as known, than to any other of the merycoidodonts. 



In the absence of the skull, however, we cannot be certain of the exact position of this genus 

 and species or whether it is independent or synonymous with one of the better known lower Oligo- 



Fig. 18. — Bathygenys alfha 

 Douglass. Fragment of left man- 

 dible. GHT. Cat. No. 708 CM. 

 Nat. size. (Redrawn from Doug- 

 lass, 1901.) 



Fig. 19. — Bathygenys alfha 

 Douglass. Right mandibular frag- 

 ment. PT. Cat. No. 708A CM. 

 Nat. size. (Redrawn from Doug- 

 lass, 1901.) 



Fig. 20. — Bathygenys alfha 

 Douglass. Crown view of superior 

 molars and fourth premolar. PLT. 

 Cat. No. 9671 A.M.N.H. Nat. 

 size. (Redrawn from Douglass, 

 1903.) 



cene forms. For the present I regard it as a dwarf form, perhaps more or less localized in Montana, 

 and with affinities in the Limnenetes-Eporeodon phylum. 



Etymology: Bathygenys (deep + lower jaw). 



Genus OREONETES Loomis 1924 

 Table 1 



Original Reference: The oreodonts of the Lower Oligocene. Ann. Carnegie Mns., XV, pp. 370-371. 



Genotype: Oreonetes ancefs (Douglass) 1901. 



Genoholotype: Cat. No. 745 CM., mainly a palate, lacking part of the muzzle. 



Distinguishing Characters: Skull small, low, and mesocephalic, with slightly arched 

 superior contour; nasals long; face longer than posterior of skull; brain case low, narrow, and 

 elongate; orbits open; frontals wide and unreduced; zygomatic arches light; bullae very small; 

 antorbital fossa large; infraorbital foramen above P 3 . 



Dentition: Brachyodont; P 4 with traces of both anterior pits; P 3 with weak median and 

 anterointermediate crest; posterior crescent well developed on all superior premolars; all molars 

 very similar to those of Merycoidodon; in lower premolars, anterior crescent undeveloped, pos- 

 terior basin enclosed by posterior crescent and median crest which unite. 



Discussion: Oreonetes is more primitive than Merycoidodon and in all probability ancestral 

 to it, since the former fulfills the requirements of a transitional form leading to the latter genus. 

 Apparently Protoreodon of the Uinta Eocene is not directly ancestral to Oreonetes nor to Limne- 

 netes, for the feet and dentition are more specialized than in either of the latter genera, as Loomis 

 (1924A, p. 370) has pointed out. 



Hay (1930, p. 755) classified Oreonetes and Limnenetes under the Dichobunida?, without stat- 

 ing any of his reasons for so doing. I consider these genera to be true merycoidodonts and classify 

 them unreservedly with that family. 



Etymology: Oreonetes (mountain + injected = subjected to mountain life). 



