PAL.EOSYOPS LEIDY, AND ITS ALLIES. 
281 
the second, there Ijeing no interval between the teeth in the superior series. The 
second preniolar is a triloliate tooth, its external lobes being eqnal, as is generally the 
case in all the superior preniolars of this species. 
The third preinolar differs from the foregoing in being larger ; its crown is 
higher, and an anterior buttress appears for the first time. The external lobes 
in this tooth show no signs of separation. The fourth premolar is an enlarged 
representative of the preceding tooth with fhe addition of an enlarged anterior 
buttress, and the separation of the external lobes by a well marked median 
fold. The anterior border of this tooth is nearly straight. In the preceding jjre- 
molar it is very oblique. In all the premolars of this species the internal 
lobes are conical, shoAv little signs of becoming concave externally, and 
have sharp lateral crests, as is seen in Tehnatotherium. The intermediate con- 
ales are absent on the premolars of this species. In the male the preniolars 
have the same general characters as already given for the female, but the trans- 
verse diameter of the third preinolar is much less than that of jiremolar 4. Its 
form is much more nearly square than that of No. 10,009. The last premolar in 
this indi\adual is a larger tooth than in the female; although, as is always the case 
with this species, the transverse diameter of the last premolar is less than that of 
the first true molar. This tooth in the male has its form more nearly rectangular 
than that of the female. In Professor Cope’s collection there is a series of superior 
molars of this species in which the premohars have much higher crowns than in the 
Ih’inceton examjjles; the external lobes are sharper and in the last premolar 
they are not separated -by a median buttress. All these characters point to the 
genus Telmatotherium, and we may consider this specimen as intermediate in char- 
acter between the typical examples of P. paludosus and Tebnatotheriiim. 
Another character of Cope’s specimen is that the superior jjremolars 2 and 3 
have complete basal internal cingula. In all the premolars of this species that I 
have examined the basal cingula are incomplete. This only proves what a variable 
character a complete or incomjilete cingidum is, and that it cannot be used for specific 
definition. We may add that in a species of Hyrachyus which I have examined, the 
same jnemolar of opposite sides had on one side a complete cingulum and on the 
other side the cingulnm was inconqilete. 
The superior molars (Plate XII, fig. 17) in this species are large, with veiy 
low crowns and their tran.sverse diameter exceeds their antero-posterior. They 
differ in this respect from those of Telmatotherium in wdiich the form of the 
molar is nearly sc^uare. In the latter genus the crowns of the teeth are very high. 
In this species the external V’s are very strongly developed, although they are 
much narrower and more concave than in Tehnatothermni. In some molars a 
median fold is present on the anterior V, although this is a variable and a primi- 
tive character. The buttresses of the external faces of the molars are very large ; 
the anterior is widely jJi’olonged beyond the posterior limit of the one in front ; the 
median buttress is low and jiromiuent, but not constricted off so much from the 
