
692 The American Naturalist. [August, 
had the dimensions of the guanaco. No genus of the family 
has been yet reported from the Eocene. 
The Astrapotheriidze include the largest forms of the Litop- 
terna, if they belong truly to this suborder. Three genera are 
certainly known, which differ as follows: 
Dentition; I. rg; C.4; Pm.4; 
M. 2; no diastema í Hlomatodontotherium Huxley. 
Dentition; I. 4; C. į; Pm.2; 
M. 4; a long diastema ; Astrapotherium Burm. 
Dentition; I. ?; C.?; Pm. 4; 
M. 3; a long diastema; Listriotherium Merc. 
In Homalodontotherium the dental series is uninterrupted, and 
the canines are small and resemble simple premolars. The pre- 
molars differ somewhat from the molars, and the molar series 

FIG. 4.—Homaladontotherium cunninghamii Flower; upper and lower dental series ; 
about two-fifths natural size. From Flower. 
generally has much the appearance of that of Canopus among 
‘the rhinoceroses. Inthe inferior molars the resemblance is not so 
great, although not wanting (Fig. 4). Nothing is known of the 
typical and only species, H. cunninghamii Flower, but the denti- 
tion, and this indicates an animal of the size of an ox. 
In Astrapotherium Burm. the dentition is much more spe- 
cialized. The canines are large, and they are followed by a dias- 
tema. There are only two premolars above and one below. The 
superior premolars differ from the true molars more than is the 
case with Homalodontotherium, but they have the same character, 
—1. e., an external wall, anda curved internal crest, the convexity 
