DISTINCTIVE CHARACTERS OF MASTODON AND ELEPHANT. 17 



tudinal line of division ; the ridges niore nnmerons and less 

 definite, each being composed of a greater number of mam- 

 millary or digital points, which are most elevated in the 

 middle, rendering the ridges convex across, instead of con- 

 cave ; the processes of enamel thinner, higher, and more 

 divided ; and the deep narrow valleys between them entirely 

 filled up with cement. The limitations of the two genera 

 agree pretty well with the views generally entertained by 

 palaeontologists regarding them ; with the exception, that 

 the group comprising the collective Mastodon Elephanto'ides 

 of Clift, and by some called ' Transitional Mastodons,' 1 is here 

 regarded as more properly belonging to the Elephants. 



A Synoptical Table 2 is annexed of the species of Mastodon 

 and Elephas, ranged under subgenera, after the manner here 

 indicated. The species were first determined or adopted 

 after a careful examination of all the original materials 

 accessible, in the foreign collections already referred to 

 (p. 4), or in various museums in the United Kingdom. 

 They were then arranged serially, according to their relative 

 affinities, as indicated by the molar teeth ; the common cha- 

 racters were next analyzed, to furnish a key for breaking up 

 the mass of species into groups representing genera and sub- 

 genera ; and the Synoptical Table shows the result. It is put 

 forward as exhibiting a fair representation of the subject, so 

 far as the materials and state of knowledge at the present time 

 admit, but with no pretension to being either unexception- 

 able or complete. The progress of investigation, by the 

 discovery either of new forms, or of more abundant materials 

 of the species which are now the most imperfectly deter- 

 mined, will in all probability modify more or less, or break 

 down, any generic or subgeneric limitations that may be at 

 present devised. For the daily experience of every depart- 

 ment of Mammalian Palaeontology tends to show that, while 

 the characters of species are persistent over wide areas and 

 through long periods of time, genera are nothing more than 

 ideal or conventional centres, around which groups of species 

 are arranged, subject to incessant modifications through the 

 discovery of new forms. It would be foreign to the main 

 object of the present communication, and beyond the limits 

 within which it is necessarily restricted, to discuss in detail 

 the grounds on which the arrangement is founded. As this 

 will be done more fully elsewhere, I shall content myself 

 here with stating them in a general way, and with indicating 

 where the assailable points are. Although the Mastodon of 



1 Owen's 'Odontography,' p. 624. (See 

 vol. i. p. 68. — Ed.) 



2 In Plates I. and II. also are figured 

 VOL. II. < 



in outline the skulls of the several 

 species of Mastodon and Elephant.— 

 [Ed.] 



