ORDER UNGULATA. 



1377 



are unknown. In Toxodon, of which the type species is of large 

 size and is found in the Pleistocene of Argentina, the dental for- 



mula is I. -, C. -, Pm. ~, M. £. All the teeth (fig. 1251) grow 



3 1 3 3 



from persistent pulps ; the lower canines are very minute, the inci- 

 sors large, and the crowns of both the latter and of the cheek-teeth 

 strongly curved. The structure of the latter is a simplification of 

 the plan obtaining in Nesodon. The femur has no third trochanter, 

 the fibula articulates with the calcaneum, and the cranium approxi- 

 mates in some respects to that of the Suidce. In the typical T. 

 platensis the outermost upper incisor is the larger of the two, the 



Fig. 1251. — Oral surfaces of the right upper (a) and lower (b) dentition of Toxodon Burmeisteri ; 

 from the Pleistocene of the Argentine Republic. Much reduced, c, The lower canine. 



reverse condition obtaining in T. Burmeisteri (fig. 1251). From the 

 infra-Pampean deposits Dr Ameghino has recently described vari- 

 ous remains of allied forms under the names of Toxodontotherium, 

 Haplodontotherium, and Dilobodon. A mandible from the Tertiary 

 of Monte Hermosa, in Argentina, is characterised by the triangular 

 form of the third incisor, and has accordingly been named Trigodon 

 by Dr Ameghino. Dr Moreno states, however, that this mandible 

 belongs to the same animal as the teeth described as Toxodontother- 

 ium and Haplodontotherium ; and he would adopt for their owner 

 the name Trigodon as the one which was alone well defined. 1 The 

 type mandible is peculiar in having only a single median incisor, 

 placed on the line of symphysis, but this is probably an individual 

 abnormality. Apparently more nearly allied to Nesodon (which Dr 

 Ameghino makes the type of a distinct family) are Colpodon and 

 Protoxodon ; while other allied remains described by the same writer 

 from the Tertiaries of Argentina under the names of Inter cither ium, 

 Toxodontophanes, and Tembotherium^ are referred to two distinct 

 families. 



Family Typotheriid^e. — Perhaps still more remarkable is Typo- 



1 This name is really preoccupied by the earlier Trigonodon and Trigonodns. 



