124 F. B. Loomis — Wasatch and Wind River Rodents. 



plump cusps being marginal and leaving a large interior 

 basin. Between the two outer cusps a small mesostylid is 

 developed. The anterior inner cusp (paraconid) is considerably 

 higher than the others. The limbs are shorter and much heavier 

 than those of a squirrel of the same length of body, this being 

 especially the case with the hind limb ; so that Paramys would 

 have approximated the appearance of a woodchuek or marmot. 

 As the limb bones are much heavier and the tuberosities well 

 developed, and as the distal end of the humerus is expanded, 

 it seems probable that these forms were terrestrial, not to say 

 burrowing forms. . The astragulus of Paramys is especially 

 broad and the articulating surface flattened, with the head 

 directed obliquely backward ; while the same bone of squirrels 

 is narrow with a deeply grooved articulating surface and the 

 head directed straight back. 



Sciuravus was founded in 1871 by Marsh* for a group of 

 tiny rodents closely related to the foregoing but clearly 

 separated by dental characteristics. ■ Like that of Paramys, the 

 skull is long and narrow especially between the orbits, being 

 there about •§- the length. There is no longitudinal crest. 

 While the general characteristics of the skull are similar to 

 Paramys, the upper molars are distinguished by having four 

 subequal cusps, the hypocone being fully developed. There 

 is no parastyle but the mesostyle is weakly developed. The 

 intermediate cusps are weak or wanting. The lower molars 

 are very low crowned, and the cusps all unusually low and 

 small, making the upper surface less irregular than in Paramys. 

 Following (p. 125) is a table to compare the three genera 

 Sciurus, Paramys and Sciuravus. 



The species of Paramys begin in the Wasatch and increase 

 in abundance to their height in the Bridger, the last of them 

 occurring in the Uinta. To facilitate the use of terms an 

 upper and a lower molar is labeled in figure 1. 



Paramys primaevus sp. nov. 



Type No. 243, consisting of two upper . jaws and parts of 

 both lower jaws together with fragments of the incisors, found 

 in the Wasatch beds of Buffalo Basin near Meeteetse, Wyo. 



Of the upper teeth premolar 4 is without an anterior," 

 marginal ridge, but the ridge from the paracone extends to 

 the protocone, the anterior intermediate being indistinguish- 

 able. The molars have the anterior marginal ridge, while 

 that from the paracone includes the anterior intermediate, but 

 does not reach to the protocone. The hypocone is merely 

 indicated. The posterior intermediate cusp is distinct though 



* This Journal (3), ii, p. 122. 



