332 
A MEMOIR UPON THE GENUS 
Superior 7 nolars, (PL XII, Hgs. 14, 15.)— Tlie true molars are of the Telinato- 
theroid type, that is with high crowns, axes nearly equal and very prominent and wide 
external lobes. The median buttresses of the molars, as in Telmatotheriiim, are strongly 
constricted off, and the external liice of the teeth are provided with a strongly marked 
cingulum. The portions of the V’s between the buttresses are flat and even, and 
there is only a slight trace of the median rib. The internal cones of the molars are 
characterized by being very iiyramidal in form, thus diftering from Telmatotherium 
where these cones are sharp and round. The protocone of the la.st molar is large 
and placed opposite the concavity of the V’s. The intermediate conules of the 
molars are only slightly developed. They all have a very small protoconule. 
and there is a rudiment of the metaconule on the last molar. Tlie intermediate 
conules are in a state of reduction in this species and in that respect are like those 
of T. cultridens in which they are nearly wanting. The posterior internal angle 
of the last molar is cut off oblicpiely, and has not the square form which is so 
characteristic of Tehnatothemmi . 
Inferior molars. — The beautifully preserved mandible figured by Leidy,' 
with the lower dentition nearly complete, we may consider as the type speci- 
men. It illustrates the characters of the lower molars in this species. This 
jaw was not found associated with any superior molars, although we find the type 
specimens of the upper molars correspond very well with it. The original iiderior 
molars which were described by Leidy,^ I have shown in my preliminary j)aper 
to belong to P. paludosus. As we have already seen, the charactei’s of the 
upper molars more closely resemble those of Telmatotherium than tho.se 
of PalcBosyops. On the other hand, the lower molai’s are more of the Pahv- 
osyops type ; that is to say, their crowns are low and hi'oad, the arms of the V’s 
are not high, sharp, and bordered by deep valleys as in Telmatotherium. Only the 
last two premolars ai-e preserved in the jaw belonging to the Academy ; in preniolar 
3 the protoconid is much larger than the metaconid, but there is no trace of the 
posterior arm of the anterior V jjresent in P. paludosus. The double I^’s of tlie last 
premolar are, however, more strongly expressed in this jaw than in that of the 
larger species. The entoconid of this tooth, as in that of P. paludosus, is wanting. 
The last inferior molar differs from that of P. paludosus in being .somewhat longer 
in proportion to its breadth. The jJosterior tubercle of this tooth agrees with that 
of Telmatothermm in being a well developed lobe, although its transverse extent is 
much less than the transverse diameter of its molar. Both the internal and 
external basal cingula are wanting in these teeth. The few specimens of this 
species in the Princeton collection show little variation in the characters of the true 
molars, and as we have seen, such variation is confined mainly to the jiremolar 
series. I may add that in all the teeth examined of P. minor the enamel is 
perfectly smooth and generally of a very dark color. 
‘Report U. S. Geol. Surv. of Terr., 1873, plate V, figures 10-11. 
‘‘Proc. Acad. Phil., 1870, page 113. 
