1897.] Toxodontia. 491 
Inferior molars turned inwards and true molars turned 
outwards ; Stenostrephanus Amegh. 
aa Molars + and y bilobate externally and internally. M. 
z trilobate on internal side, Lithops Amegh. 
Of the six species of this family one of Lithops and one of 
Stenostephanus are from the Lower Eocene of Patagonia; and 
one of Entomodus, one of Xotodon and one of Stenostephanus 
are from the Lower Miocene of the same region ; and one spe- 
cies of Xotodon is from the Upper Miocene of Buenos Ayres. 
The Toxopont1p includes the latest of one of the two lines 
of descent of this order. The genera differ in the forms of the 
molar teeth, and some of them show a decided simplification 
of structure which must be regarded as a degeneracy. Most 
of the species are of large size. Toes three, both in front and 
behind. The genera differ as follows :— 
I. Seven superior molars. 
Superior molars with internal groove and column of mod- 
erate size ; Toxodon Owen. 
Superior molars with internal groove and very large in- 
ternal column ; Toxodontotherium Amegh. 
Superior molars without internal groove or column ; 
Haplodontotherium Amegh. 
II. Six superior molars. 
Pm. 4 and true molars with two internal grooves ; 
Dilobodon Amegh. 
Pm. all simple; m. with one internal groove; 
Trigonodon Amegh. 
Seventeen species of this family have been determined up 
to the present time, eleven of which belong to the genus Tox- 
odon. Two species each are referred to Toxodontotherium 
and Dilobodon, and one each to the two remaining genera. 
The geological distribution of these species is as follows :— 
Oligocene. Miocene. Pliocene. 
Toxodon, ` 1 7 
Toxodontotherium, 
oe ANE deen au eae 
m bo Co 
Dilobodon, 
Trigonodon, 1 
~J 
[S] 
o | 
s 
