326 PROCEEDINGS OF THE ACADEMY OF [1892. 



place in any other species referred to Hippotherium. In both these 

 stages the enamel borders of the lakes are more or less plicate, and 

 the posterior loop of the anterior lake is present. With further 

 wear the plications, including the loop, disappear, when the molars 

 agree in their characters with Protoluppus parvulus Marsh. These 

 observations were based on specimens from the Loup Fork beds 

 of Nebraska, Kansas, Colorado and Texas, where the species is 

 abundant. 



The speaker exhibited the molar dentitions of three colts from 

 Wyoming and Texas, and a part of one from Colorado, all from the 

 Loup Fork beds. He showed that these represent the genera 

 Merychippus, Parahippus, Hypohipjjus, and Anehippus of Leidy, 

 and six species of the same author. He thought it probable that 

 Anchipqms belongs to a colt of Hippotherium, and Parahippus and 

 Hypohippus to Protohippius, while he was not certain as to the 

 reference of the type of Merychipptis (31. insignis). He pointed 

 out that the characters of the individual temporary molars differ in 

 the different teeth of the series, and also differ at different stages of 

 wear. As with the permanent dentition, in some species the tem- 

 porary molars are always simple, while in others the enamel borders 

 are more complex. In the latter case the pattern becomes more 

 simple in some respects with prolonged wear. He was able to 

 correlate the temporary and permanent dentitions of Protohippus 

 perditus Leidy with certainty, and those of P. jxichyops Cope and 

 P. mirahilis Leidy with much probability. 



Professor Cope further pointed out that the temporary dentition 

 in these three-toed horses is more simple than that of the adult, in 

 some cases resembling very closely the permanent dentition of the 

 ancestral Anchitherium in molar structure. In this the horses 

 difl^er from the higher Artiodactyla, where the temporary molars 

 are equally complex or more so than the permanent molars. 



October 11. 



Mr. Charles Morris in the chair. 



Forty-three persons present. 



A Hyena and other Carnivora from Texas. — Prof. E. D. Cope 

 stated that he had during the past season while exploring the eastern 

 front of the Staked Plains of Texas with a party of the Geological 

 Survey of that State under Prof W. F. Cummins, obtained the 

 remains of some interesting Carnivora from the Blanco or Pliocene 

 beds. One of these is a hyena nearly allied to the genus Hyoina, 

 and the first species of this family found in America. It, however, 

 differs from the typical genus in having a fourth premolar in the 

 lower jaw, and probably in having a shorter blade of the sectorial 

 tooth in the upper. He proposed the name Borophagus for the 

 genus, and for the species the name diversidens. The third premolar 



