1887.] ^^^ [Cope. 



theriuin and Mixochcerus of Filhol. But the structure of the feet of the 

 latter geuera is unknown. In Mixtotherium the fourth premolar is more, 

 and the others less complex than in Anoplotherium. 



The known genera of Dichobunid.e are Dichobune of Cuvler, with 

 Spaniotherium and Dilotherium of Filhol, in which the. intermediate tu- 

 bercles are less developed than in Dichobune. They are related to the 

 two selenodont genera of C^notheriid^, Ca^notherium and Muillacthe- 

 rium. Tlie latter differs from the former in the absence of the intermediate 

 crescent from the last superior molars. The species of Ca?notherium differ 

 in the absence or presence of a short diastema in the dental series, and in 

 its position in the lower jaw, whether behind the first or second premolar. 



The Dichobunid bunodout geuera are ancestral to the Ca3notheriid sele- 

 nodont genera in the following fashion : 



Cajnotherium Muillactherium 



Spaniotherium 

 Dilotherium 



Dichobune 



This family terminated with the selenodont genera, which, as Schlosser 

 remarks, left no known descendants. 



The ANTHRACOTHEniiD^ present but few variations. Four genera are 

 known, which differ as follows : 



Entirely bunodont ; no diastemata ; canines developed. Geboch(Krus Gerv, 

 Cusps of superior molars little flattened ; diastemata ; canines large 



Choiropotamus Cuv. 

 Cusps of superior molars flattened ; no diastemata ; canines large 



Anthracotherium Cuv. 



Cusps of superior molars crescentoid in section ; diastemata ; canines large 



in males Hyopotamus Owen. 



The three genera last named cannot, as Schlosser remarks, be related in 

 direct lines, but through cbmmon ancestors ; as may be shown thus : 



Hyopotamus 



Anthracotherium 

 Choeropotamus 



Cebochcerus 



