1881.] 181 [Cope. 



are more elevated than in the other species, and those of the external side 

 all have a distinctly crescentic section. The anterior inner cusp is narrow 

 and simple. There is no cingulum of any kind. 



This species was originally described from New Mexican specimens. 



Phenacodtjs I/Atictjneus, sp. nov. 



This is the least species, and is represented by six superior molars and 

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

 exhibits peculiar characters already mentioned. The superior molars 

 differ from those known to belong to the P. primcevus 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 Anisonchus, but the important difference remains 

 in the separation of the anterior inner tubercle from the intermediate 

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



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

 in section, their external sides forming a convex rib. There is no rib 

 between the external sides. There is a strong anterior cingulum, which 

 terminates externally in a low angular cusp. There is no cingulum on 

 any other part of the crown. The second, third and fourth premolars have 

 two external cusps, and much resemble the corresponding teeth in Hyraco- 

 therium. The second is longer than wide, and has an internal ledge ; the 

 third is as wide as long and has a wide internal ledge ; the fourth is wider 

 than long and has an internal, and two intermediate cusps, and an anterior 

 and posterior cingulum. They all have a weak external cingulum, of 

 which a trace exists in the true molars. 



The last inferior molar has a double anterior inner cusp as in some 

 Mesodonia, and the external anterior cusp is robust. All the cusps are 

 conical and with round section, and their bases are close together. The 

 outline of the base of the crown is almost an isosceles triangle with rather 

 wide base in front. 



Measurements. M. 



Length of last six superior molars 0350 



" true molars 0160 



_. .„.. T _ r anteroposterior. 0055 



Diameters of M. II J ^ aao . 



( transverse 0080 



Long diameter base of P-m. II 0050 



_. _, TTT r anteroposterior 0060 



Diameters P-m. Ill 1 * nrxnn 



\ transverse 0060 



' Anacodon tjrsidens, gen. et sp. nov. 



Char. gen. Known only from mandibles supporting molar teeth. Prob- 

 ably family Phenacodontidce. Last inferior molar with heel. Crowns of 

 molars without distinct cusps, but with a superior surface consisting of 

 two low transverse ridges separated by a shallow valley. Unworn grind- 

 ing surface with shallow wrinkles, Perhaps only three premolars. 



