314 
PEOBOSCIDEA. 
Nebraska belongs ; but the majority of American Mastodons are congeneric 
with the present species. Seven species of this genus are recorded by 
Falconer, and there maybe added, as discovered in North America since he 
wrote, the species M. ohscurus and M. shepardii of Leidy and M. proavus of 
Cope. There is also the M. cJiapmanii of Hays,* which has not been recently 
observed. The M. productus, belonging to that section of the genus in 
which the transverse valleys are interrupted by tubercles or cones, com¬ 
parison with the Mastodontes Jjorsonn, tapiroides, oJdGticus, proavus^ and 
shepKirdii is unnecessary. Among the species where tlie lateral cones are 
accompanied by others which interrupt the valleys, M. liumboldtii and M. 
(indium possess a short contracted symphysis without tusks. M. angusti- 
dens possesses the produced symphysis with tusks, and is also a species which 
stood on long limbs, like the M. prodiictus and the living Elephants. The 
M. productus differs from it in well-marked characters, according to the 
descriptions of the latter which have been given by Dr. Falconer. This 
author states that the mandibular ramus of M. angustidens is much elevated, 
in front, and most above the mental foramen. In Af. productus, the eleva¬ 
tion at the mental foramen is barely equal to the depth at the base of the 
coronoid process, while the elevation is greatest between these points at 
the anterior base of the penultimate molar, and it is not so great as in the 
European species. The symphyseal prolongation is not so long in M. pro¬ 
ductus, equaling fo the mental foramen (without the tusks) two-thirds the 
length of the remaining portion to the base of the coronoid jmocess. Dr. 
Falconer says of the M. angustidens, “The elongation of the symphyseal 
beak is enormous, far exceeding that of Tetralopliodon longirostris or even of 
Dinotherium; the length from the mentary foramen forward being more 
than double that of the horizontal ramus measured from the same point 
Ijackward to the base of the anterior margin of the coronoid process.” 
According to the same writer, the symphyseal tusks of M. angustidens fre¬ 
quently have a channel on the superior and inner sides. In M. productus, 
the tusk is without channels. 
Besides the generic character in the tooth-formula, this species differs 
from Tetralophodon longirostris in the form of the base of the symphysis. 
* Trans. Amer. I’Lilos. Soc., 1^33, pi. xxii, ligs. 3-4. 
