THA EXTINCT PECCARY OF NORTH AMERICA. 101 
symphysis is narrow and keeled, the incisor teeth are smaller, and the principal lobes of 
the molar teeth possess a greater proportionate degree of development. 
Comparison in the varieties of dentition observed in Dicotyles compressus.—In figures 5, 6, 
plate 37 of volume X. of these Transactions, is given a representation of the right upper 
series of molar teeth, of the cave head, formerly viewed as characteristic of Huchocrus macrops. 
The teeth may be observed to be constructed on the same plan as those of the recent pecca- 
ries, but strikingly to differ in the greater degree of development of their primary lobes. 
In figure 2, plate 6, accompanying this communication, is represented the corresponding 
series of teeth, from the Iowa fossil in possession of Dr. Wyman. These teeth have 
slightly more robust proportions than those in the cave head; and they also belong to an 
adult individual, whereas in the latter, the permanent premolars and last true molar, had 
not yet protruded from the gums. The crown of the last true molar in the Lowa fossil, 
is less narrowed posteriorly than in that of the cave head, its postero-external lobe is pro- 
portionately with its fellow much better developed, and the basal ridge does not extend ex- 
terior to the latter, as it does so conspicuously in the cave head. In the preceding true 
molars, the lateral offsets of the inner lobes are rather better developed than in the cave 
head. The crowns of the premolars have rather different outlines in the two fossils; and 
in the case of the first of the series, it is trilateral in the fowa specimen, and quadrilateral in 
the cave head. In the last two premolars the thick basal ridge continues around the inner 
side in the former, as in the first premolar, but does not do so in the cave head. 
In the imperfect series of isolated upper molars, represented in figs. 12, 13, plate 
37, volume X., formerly referred to Platygonus compressus, a condition is observable in the 
last two true molars, so different from that in the teeth just disposed of, that if they had 
been discovered unassociated with congeneric remains, almost any naturalist would have 
supposed they belonged to a taperoid, rather than to a dicotyline animal. The crown of 
the last true molar, has its unsymmetrical lobe in a most rudimental condition; and it has 
a quadrilateral oval outline instead of being trilaterally ovoidal. In this and the preceding 
tooth trituration has advanced more in clearing out the transverse valleys, than in wearing 
away the summits of the lobes, so that the teeth have assumed an appearance resembling 
that of the inferior molars of the Tapir, whereas in the recent peccaries ordinarily, and 
as is also observable in the corresponding teeth of the Iowa fossil, fig. 2, plate 6, the sum- 
mits of the lobes are worn away without clearing out the transverse valleys. These facts 
would lead to the supposition that we really had before us the remains of two distinct gener 
of animals in which the trituration of the teeth proceeded on a different plan, but an inspec- 
tion of the first and second true molars in the cave head, and the inferior true molars of 
Dicotyles compressus led me to view the difference as only another individual peculiarity 
