490 THE WASATCH EPOCH. 



Phenacodus macropternus Cope. 



Paleontological Bulletin, No. 34, pp. 179-180, Feb. 20, 1682. 

 Plate XXV e; fig. 15. 



This species is apparently rare, being represented by only one man- 

 dibular ramus, which supports the posterior three molars, and a possible 

 second ramus with molars iv and v. The first and second true molars are 

 much like those of P. vortmani, but the third is relatively larger, and has an 

 especially elongate heel. In P. vortmani the last molar is constricted, and 

 narrower than the penultimate. In P. macropternus there is a weak external, 

 and no internal cingulum. The tubercles of the last two molars are quite 

 regularly conical, while the external pair of the first molar wear into cres- 

 cents. Smaller than the P. vortmani. 



Measurements. 



u. 



Diameter8M.i|''°*«^°P°«*«"'*'" °^f^ 



( transverse U05U 



_.. J. nr ••■< anteroposterior 0095 



Diameters M. Ill ^ ^ .... 



( transverse uubo 



Depth of ramus at M. ii 0130 



From the Wasatch of the Big Horn, Wyoming ; J. L. Wortman. 

 Phenacodus brachypternus Cope. 



Paleontological Bulletin, No. 34, p. 180, Feb. 20, 1882. 

 Plate XXV e; &g. 14. 



Three mandibular rami are the only specimens of this species found 

 by Mr. Wortman in the Big Horn region. They all display the fourth pre- 

 molar, which has the characters of this genus, as distinguished from 

 Mioclcemis. The species is materially smaller than the P. vortmani, and its 

 last inferior molar is intermediate between those of the latter and the P. 

 apternus, in form. Both the internal and external intermediate tubercles 

 are very full, and give the tooth posterior width. The posterior or fifth 

 tubercle is large, and gives the posterior outline of the crown a trifoliate 

 form. The posterior median tubercles of the M. ii and i are well marked. 

 The molars gradually increase in size forwards, and the fourth premolar is 

 longer than any of them, and rather narrow. Its form is more elongate than 

 that of any other species, as it has a well-developed anterior lobe. It is 



