MESODONTA. 231 



tutus that I am induced to refer them to the P. frugivorus, with which they 

 agree in size. They differ from those of P. delicatissimus in possessing an 

 external basal cingulum and only one principal external cusp of the fourth 

 premolar. The posterior molar is also abbreviated posteriorly, as in P. 

 tutus. As compared with that species, the intermediate tubercles are less 

 distinct, though present, and the inner basal cingula are weaker. The fol- 

 lowing measurements show the smaller dimensions: 



Measurements. 



M. 



Leogth of last four superior molars 0160 



Diameter8fourthpreinolar^='°*eropo8terior .00:« 



< transverse 0055 



Diamteters second true molar J ''°^<''°P''^**"0'^ 0050 



( transverse 0070 



Diametersthirdtruemolar^''"f^""P''^*''"'"' " - -OO^" 



( transverse 0058 



The infraorbital canal is contracted and long, and issues above the 

 third premolar. This proves the fragment not to be rodent. 



This species is abundant in the Big Horn bad lands. Mr. Wortman 

 obtained there two entire mandibles and seven separate rami which agree 

 in all respects with the typical specimens. He obtained three mandibular 

 rami in which the molar teeth measure .016 in length; that is, intermediate 

 between the P. frugivorus and the P. tutus. Of the latter species Mr. Wort- 

 man discovered four mandibular rami. One ramus shows a length of .018 

 for the true molars, which are therefore intermediate in size between the P. 

 tutus and P. jarrovii. It will be necessary to study other parts of the skel- 

 eton in order to ascertain the status of these individuals. 



Pelycodus angulatus Cope. 



Systematic Catal. Ent. Vert. Eocene, New Mexico. U. S. Geog. Surv. W. of lOOth Mer., 1875, p. 14. Re- 

 port U. S. Geog. Siirv. W. lOOth Mer. iv, pt. iii, p. 144, pi. xxxix, fig. 15. 

 Plate XXIV d; fig. 4. 



The P. angulatus, originally known from New Mexico, is represented 

 in the Big Horn collection by four mandibular rami, and a portion of a 

 maxillary bone with teeth. 



The inferior molars present much the appearance of those of the larger 

 species. The anterior inner cusp is well developed, and nearly on the inner 

 border of the crown, though not so large as the other anterior cusps. The 



