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IV. — On the Evolution of the Proboscidea. 



By C. W. Andrews, D.Sc, F.G.S., British Museum (Natural History). 

 Communicated by Prof. Ray Lankester, F.R.S. 



Received March 5 —Read March 26, 1903. 



The Proboscidea form one of the most isolated groups of the mammalia, for although 

 it is now generally recognised that they belong to the Ungulata, they nevertheless 

 differ widely from all other members of that order. They are further remarkable for 

 the fact that, while in some respects, e.g., in their large size and peculiar dentition, 

 they are among the most specialised of mammals, in others, as, for instance, in the 

 structure of their feet, they are relatively very primitive. The history of such an 

 isolated group is necessarily of exceptional interest, and the peculiarities of the 

 animals themselves render it the more easy to follow the course of their development, 

 because the danger of confusing them with allied types is to a great extent 

 eliminated ; furthermore, in scarcely any other group can the phylogenetic history be 

 traced back through so long a series of forms. 



Until quite recently the earliest Proboscidea known were from the lowest Miocene 

 beds (Burdigalien) of France, where they are represented by at least two species, viz., 

 Dinotherium cuvieri and Tetrabelodon angustidens* In somewhat later deposits 

 these two genera Dinotherium and Tetrabelodon occur widely distributed in Europe 

 and as far east as India. Tetrabelodon angustidens has also been recorded from the 

 northern part of the Libyan Desert and from Morocco. The group seems to have 

 reached North America during the Miocene, and the earliest recorded species is found 

 in the Upper Miocene beds of Montana. This form has been described by Cope under 

 the name Tetrabelodon brevidens ; it is remarkable for the simplicity of its molars. 

 Dinotherium is not found in any American deposits. The Mastodons did not penetrate 

 into South America till the Pliocene. The absence of Dinotherium from America and 

 the circumstance that the teeth of Tetrabelodon brevidens are at least as simple as 

 those of any European species, suggests the possibility that the Proboscidea may 

 have reached North America not by way of Europe, but along some independent land 

 connection. The absence of the dinotheroid type might also be accounted for by the 



* This name is here adopted in preference to the more usual one, Mastodon angustidens, because there 

 can be no doubt that this animal is generically distinct from the Mastodon americawus for which the genus 

 Mastodon was founded by CuviER, and falls within the genus Tetrabelodon as denned by Cope. 



VOL. CXCVI. — B. 217. 2 13.8.03. 



