492 THE WASATCH EPOCH. 



DIACODEXIS Cope. 



American Naturalist, 1882, p. 1029. (Dec. 2 (»).) 



Inferior and superior molars tubercular; the superior with interme- 

 diate tubercles, but no external cingular tubercle. Principal external cusps 

 subconic; the anterior internal cusp continuing into the anterior interme- 

 diate on trituration. There are four superior premolars, of which the 

 posterior three have two external cusps. The third and fourth have well- 

 developed internal lobes. The inferior premolars and molars are unknown, 

 except the last true molar. This has distinct cusps, not joined by crests, 

 and a prominent heel or fifth lobe. 



It is yet to be positively determined whether this genus belongs 

 among the Condylarthra or with Pantolestes in the suilline Artiodactyla. It 

 somewhat resembles Dichobime, but differs in the absence of the interme- 

 diate crescentic lobe of the superior molars, and the development of a trans- 

 verse crest on wearing. These teeth are in fact like those of the Perisso- 

 dactyla, and this fact, together with the bunodont type of the true molars, 

 induces me to place the genus provisionally in the Phenacodontidce. 



But one species is known, which is from the Wasatch formation. 



DiACODEXIS LATICUNEUS CopC. 



American Naturalist, June 1882, p. 1029. (Dec. 2(?).) Phenacodus laticiineus, Paleontological Bulletin 



No. 34, 1882, p. 181. 

 Plate XXVe; figs. 17-18. 



This is a small species, and is represented by six superior molars and 

 the last inferior molar in a fragment of the lower jaw. The latter tooth ex- 

 hibits peculiar characters already mentioned. The superior molars differ 

 from those known to belong to the Phenacodus primmvus and P. puercensis 

 in having a vertical fissure of the inner side which separates the bases of 

 the two internal tubercles. This gives them some resemblance to the 

 superior molars of the species of AnisonclmSy. but the important difference 

 remains in the separation of the anterior inner tubercle from the inter- 

 mediate tubercles. The three are confluent into a V in the genus last 

 mentioned. 



The external cusps of the superior molars are rather acute, and lentic- 



