'Cope.] 4b^ |- 0ct 20, 



CHORISTODERA. 



Champsosaurus australis Cope, American Naturalist, 1881, p. 690. 

 Champsosaurus puercensis Cope, Proceedings American Philosophical 

 Society, 1881, p. 195. 

 Champsosaurus saponensis Cope, Loc. cit. 1881, p. 196. 



MAMMALIA. 



MARSUPIALIA. 



Ptiloclus mediaevus Cope, American Naturalist, 1881, p. 92.2. 

 Ptilodus trovessartianus Cope, loc. cit. 1882, p. 686. 

 Catopsalis foliatus Cope, loc. cit. 1882, p. 416. 

 Catopsalis pollux Cope, loc. cit. 1882, p. 685. 

 Polymastodon tabensis Cope, loc. cit. 1882, p. 684. 



BUNOTHERIA. 



Taeniodonta. , 



Hemiganus vultuosus Cope, loc. cit. 1882, p. 831. 

 Tceniolabis scalper Cope, loc. cit. 1882, p. 604. 



TlLLODONTA. 



Psittacotherium multifragum Cope, 1. c, 1882 p. 156. 

 Psittacotherium aspasice Cope, Proceed. Amer. philosophical Society, 

 1882, p. 192, (1882). 



Mesodonta. 



Pelycodus pelvidens Cope, Proceeds. Amer. Philos. Soc. 1881, (1882) p. 

 151. Lipodectes pelvidens Cope, American Naturalist. 1881, p. 1019. 



Hyopsodus acolytus Cope, sp. nov. 



This the least species of the genus, is also the oldest, heing derived from 

 the Puerco horizon. Parts of two individuals furnish the characters of 

 the inferior and superior true molars, and the fourth superior premolars. 

 The species differs from those hitherto described in other characters than 

 the minute size. One of these is the absence of posterior interior cu6p, the 

 heels of the first and second true inferior molars being bounded by a ridge 

 only at this point, as in most of the species of Pelycodus. The last inferior 

 molar is not smaller than the second, nor longer. The anterior cusps of 

 all the molars are robust, so that on the first and second true molars they 

 are separated by a shallow notch only. There is a rudiment of the anterior 

 inner cusp on the first true molar but none on the second and third. The 

 posterior external .is obtuse and has a triangular section on all the molars ; 

 a crest is continued from the heel of the third molar on the inner side of 

 the crown half way to the anterior inner cusp. 



