PROBOSCIDEA. 
315 
Tlic inferior surface is a decurved continuation of the base of the ramus, 
as in M. angustidens, while in T. longirostris of Kaup the border of the 
ramus rises upward to the base of the symphysis. 
Two specific names have been proposed for Mastodons whose remains 
are supposed to have been found in the United States. In each case, the 
name rests on an incomplete posterior molar tooth. One of these is the M. 
chajgmanii^ Hays, of uncertain locality. The arrangement of the cones of 
the crown differs materially from that seen in M. productus^ for they are 
closely packed, almost closing the intervening valleys, as in the species of 
Tetralophodon. The cones of opposite sides are very unequal, and some¬ 
what alternate, and the enamel borders are much lobate, all characters not 
found in M. productiis. As regards tlie other species, M. obscurus, Leidy, 
Professor Leidy remarks that it may be the same as the 31. cliapmanii, but 
the existing evidence is not conclusive in favor of this view. It reposes on 
the cast of a tooth said to have been taken from the Miocene marl of 
Caroline County, Maryland.* It probably supported four transverse crests; 
but this is not certain, as the anterior extremity is broken away. In its 
constitution, it bears some resemblance to the last inferior molar of M. 
productus, but presents well-marked differences. It is narrower, the greatest 
width entering the length 2.5 times, while in all the corresponding teeth of 
the latter species the width is one-half the length. The second transverse 
crest in the type of 31. obscurus., though but little worn, does not display 
the separation into opposite cones, which, in 31. productus, is maintained 
nearly to their base; the Avorn section presenting, therefore, two areas, the 
one trifoliate, the other elliptic. In 31. obscurus, the cones of opposite sides 
display a stronger tendency to alternation, and are generally less tubercular, 
differences by themselves perhaps unimportant. I, however, suspect this 
tooth to represent a species different from the 31. productus characterized 
among other points by its narrower teeth. The discovery of the mandible 
and other bones will be necessary before it can be regarded as well estab¬ 
lished. 
Another tooth figuredf by Dr. Leidy resembles the molar of 31. pro- 
* Extinct Mammalia of Dakota and Nebraska, p. 215, pi. xxvii, fig. 13. 
ILoc. cit., xxvii, fig. 15. 
