SYNONYMS. 



235 



But an impression existed among palaeontologists in Ame- 

 rica that there might be distinct species. Dr. Warren, in 

 1855, expresses it thus : ' We still remain without any de- 

 cisive fact calculated to determine whether the American 

 varieties differ specifically from the European, and whether 

 these varieties differ specifically from each other.' ! In 1852, 

 Leidy, in the introduction to the ' Fossil Fauna of Ne- 

 braska,' 2 designates the fossil Elephant of North America 

 E. Americanus, as distinct from E. primigenius. But he gives 

 no diagnostic characters, and assigns no reason for the 

 change, which appears to be founded mainly on the sup- 

 posed improbability of the same species having ranged from 

 Europe to America. His E. imperator he assumes to be 

 distinct, ' because it was found in association with a Fauna 

 very distinct from any previously noticed' (antea, p. 230). 

 He separates the Megatherium of North from that of South 

 America, avowedly on these grounds ; and it would appear 

 that he distinguishes his Eguus fraternus and E. complicatus 

 from the European forms called E. primigenius (sic) 3 and E. 

 plicidens, on the same principle. 4 But the practice is open 

 to grave objections. It assumes a difference on theoretical 

 grounds, where the direct evidence, so far as it goes, indi- 

 cates the contrary ; and its general adoption would tend to 

 arrest, on the threshold, the investigation of the means 

 through which remote geographical forms, presenting com- 

 mon characters, may have started from a common origin. 



The separation of some of the American Pleistocene Horses 

 and Bisons from the European fossil species may prove, on 

 the comparison of sufficient materials, to be well founded. 

 But as regards the true Mammoth, E. primigenius, exclusive 

 of E. Columbi, I am satisfied that it rests on no sufficient 

 grounds. The well-known characters, upon which Cuvier 

 established his definition of the species, have been confirmed 

 by the general observation of palaeontologists up to the 

 present day, namely : the cranium long, with a concave 

 forehead, and very elongated tusk-sheaths ; the lower jaw 

 rounded, with a rudimentary beak; the molar teeth very 

 broad relatively to their length, and the constituent layers 

 of ivory, enamel, and cement very thin and condensed. The 

 definition was good, in consequence of its including so many 



1 On 'Mastodon Giganteus,' p. 161. 

 Agassiz, at the Cambridge (U. S.) meet- 

 ing of the American Assoc, for the 

 Advancement of Science, 1849, described 

 the molar and tusk of an Elephant, 

 found at Vormont in digging the Rutland 

 and Burlington Railway, and said to 

 have been from below the Erratic boulder 



drift, which from recollection he believed 

 to be different from the European Mam- 

 moth (p. 100). 



2 Op. cit. p. 9. 



3 E.fossilis. 



4 Proceed. Acad. Nat. Scion, of Phila- 

 delphia, 18.58, p. 11. 



