216 THE AFFINITIES OF TOXODONS CHAP. 
There is no doubt about the close alliance of the two genera 
just referred to. It is more doubtful whether Homalodonto- 
therium and its alles should be placed, as they often are, in the 
neighbourhood of the Toxodonts. Momalodontotherium owes its 
name to its even row of teeth without a diastema. It was a 
creature of equally large size with Zoxodon, and also came from 
the Tertiary strata of Patagonia. The teeth are the typical forty- 
four, and the molars like those of a Rhinoceros; they are, how- 
ever, brachyodont and not hypselodont as in Zowodon. This genus, 
however, shows an important difference from the Rbinocerotidae 
and from the other Toxodontia in the fact that it was five-toed, and 
that the bones of the carpus and tarsus are set in relation to each 
other in the linear serial fashion. 
Undoubtedly a near relative of Homalodontotherium is Astrapo- 
therium. ‘This creature was of equal bulk, and was also Patagonian 
in range. The teeth are reduced in number, but the animal was 
provided, hke a Wild Boar, with great tusks, which were, however, 
formed by the incisors. This animal is very imperfectly known ; 
it is the form of the molars and the large size of the incisors which 
have led to its association with the Toxodontia. As to the resem- 
blance of the teeth of this genus and of Homalodontotherium to 
those of Rhinoceros, it is difficult to regard it as evidence of near 
affinity. The likeness is probably to be looked upon as a case of 
parallelism in development. Exactly the same explanation is 
possibly to be given to the likeness which the teeth of Toxodon 
and Nesodon show to Rodents, or even to Edentates. As to their 
affinities Zittel observes :— 
“The entirety of their osteological characters argues for the 
Toxodon a separate position in the neighbourhood of the Perisso- 
dactyla, Proboscidea, Typotheria, and Hyracoidea. The relations 
to the Rodentia rest mainly upon the converging development of 
the teeth, not upon true relationship.” 
SuB-OrDER 6. PROBOSCIDEA. 
Large vegetable-feeding animals, usually scantily covered with 
hair, and with the nostrils and upper lip drawn out into a long 
proboscis. Digits five on both limbs. Femur and humerus not 
bent upon lower leg and fore-arm in a position of rest. Skull 
