1897.] Toxodontia. 487 
The molar teeth in this order are furnished with enamel 
over the summit of the crown, and in bands on its shaft, when 
present. In the superior molars there is a longitudinal ex- 
terior wall, and from one to three more or less oblique trans- 
verse crests running inwards from it, when the crowns are not 
entirely simple. The summit of the crown is soon worn away 
and the tooth then displays the pattern of a transverse section. 
The inferior molars are much narrower than the superior, and 
have several lobes on the internal side (in section). The in- 
cisors are more or less specialized towards gliriform types in 
the later genera. The canines are always small when present. 
There are but two certainly known genera of ATRYPTHER- 
11D&, which differ as follows :— 
Pm. x with four roots; two molars with open roots; an infe- 
rior canine; Atryptherium Amegh. 
Pm. ; and ; and m. ; with four roots; m. and m. with open 
roots; no inferior canine ; Scopotherium Amegh. 
Each of the above genera contained but a single species of 
about the size of a tapir, from the Eocene beds of Patagonia. 
The genus Nesodon Owen from the same region and horizon 
may be identical with Scopotherium, according to Ameghino, 
but the structure of the roots of the inferior molar is unknown. 
Two species are known, N. ovinus, the size of a sheep, and N. 
imbricatus Ow. as large as a tapir. In all of these forms the 
incisors are not much specialized, but are subequal. 
In the ĪNTERATHERIIDÆ the incisors are still unspecialized 
in the gliriform direction, and ‘their roots are conic and closed. 
The four genera differ as follows :— 
I. Pms. 2 and y with distinct roots. Incisors diminishing in 
size externally ; Interatherium Moreno. 
II. All molars rootless and open. 
Pm.s and z consisting of two subequal columns; incisors 
diminishing outwards; Icochilus Amegh. 
Pm. s and ; of two columns, the anterior much larger 
than the posterior; external incisor with expanded 
crown, which is bilobate on the internal side; 
Protypotherium Amegh. 
