1066 The Perissodactyla. [Dec. 
above; from White 
31. Symborodon trigonoceras Cope, lower jaw from s, 
«“ Report U. 
Fic. 
River beds of Colorado; one-fifth natural size. Original; from 
C 
Geol. Survey Terrs.” (unpublished). 
nodus angist- 
Transitional between the two genera is the Me 
genis Cope, from the White River bed of Canada, which ger | 
lower incisors of Menodus, with the narrow symphysis ne 
known species of Symborodon. The phylogeny of the fam 
can be thus represented : 
Symborodon. : 
Menodus. 
Diacodon. Diplacodon. | 
Ectocium. 
A genus, probably of this family, has been descr! a 
Transsylvania, under the name of Brachydiastemather! get 
a -it has not yet been clearly distinguished from the known a 
