Note 284 — Chapter IX · THE ORDER UNGULATA (continued 4)

This, and the larger number of ridges in the latter, are the only absolute distinctions which Falconer could find between Mastodon and Elephas (Palæont. Memoirs, ii. p. 9), and it is clear that they are somewhat arbitrary. The line between the two genera is drawn at this point more as a matter of convenience for descriptive purposes than as indicating any great natural break in the sequence of modifications of the same type.