28 PROCEEDINGS OF THE NATIONAL MUSEUM vol. 91 



crest extending from the paraconid down to a weak inner cingulum 

 around the metaconid as in Oxyacodon. The form resembles Oxya- 

 codon and differs fi-om EUipsodon in having relatively high, distinct 

 cusps, and M3 is unreduced in size. However, the hypoconulid is not 

 so well dcA'eloped as in the lower molars of Oxyacodon, and in M3 

 it is more reduced and less distinctly separated from the entoconid. 

 The teeth are slenderer than in O. priscilla and show no ma,rked 

 cingula on either the lingual or buccal surfaces, except for one of the 

 third molars, No. 15542, which has a slight cingulum on the outer 

 surface. 



Litomylus dissentaneus from the Crazy Mountain Fort Union ex- 

 hibits characters close to those seen in Oxytomodon perissuTn, par- 

 ticularly in the sharpness of the cusps, but the paraconid in the 

 lower molars of L. dissentcmevs is much reduced and median in 

 position. 



The anteroposterior and transverse diameters of M2 in No. 16183 

 are 3.5 and 2.7 mm., respectively. The transverse diameter of M3 

 is 2.4 mm. 



Genus ELLIPSODON Scott 



ELLIPSODON SHEPHERDI" Gazin 



ElUpsodon shepherdi Gazin, 1939b, p. 283. 



EUipsodon shepherdi is comparatively well represented in the 

 Dragon fauna. The collection now includes about 55 specimens com- 

 prised of isolated teeth and lower jaw and maxillary portions having 

 one or more teeth. 



This species, as indicated by the type lower jaw (fig. 16, a), is 

 slightly smaller than EUipsodon lefnuroides, and the molars, M2 and 

 M3, are relatively narrower. M3 is reduced to about the same extent 

 as in E. lemuroides, more reduced than in the smaller forms, E. 

 aequidens, E. acolytus^ and E, aquilonius^ but less reduced than in 

 the Puerco species, E. priscuSj and possibly somewhat less reduced 

 than in the genotype, E. inaequidens. The paraconid of the last 

 two lower molars is more distinct in the Dragon form than in any 

 of the previously known species of EUipsodon.. much better developed 

 and more lingually placed than in E. aequidens^ but only slightly 

 more prominent than in E. aquilonius. The talonids of Mg and M3 

 are more distinctly basined than in Torrejon material referred to 

 E. inaequidens., but less distinctly basined than in E. aquilonius from 

 Montana; also, the talonid on M3 is better developed than in the 

 Puerco form E. priscus. Moreover, the talonid of Mo in E. shepherdi 

 does not exhibit so prominent a hypoconulid as in E. aequidens., but 

 shows a more distinct entoconid than in E. inaequidens. 



" Named for Harold Shepherd, in recognition of his field assistance. 



