PAL.EOSYOPS LEIDY, AND ITS ALLIES. 
331 
in some respects they retain certain very primitive characters which prove the 
intermediate position of this species. 
Dentition. — The incisors are not round in section as in P. paliidosus bnt 
strongly compressed, with a rndimentaiy internal basal ridge. In the second 
incisor there is a lateral heel. The characters of the incisors are intermediate 
between those of P. paliidosus and Telmatotheriuni. In Prof Leidy’s report' he 
describes two series of superior molars associated with their canines. He notices 
the difference in the size of the canines in the two series, as well as the character 
of the preniolars in both specimens, and he concludes that the great difference dis- 
played in the size of the canines is probably a sexual character. He also remarks 
that with the great development of the canines there is a concomitant reduction, as 
it were, of the premolars. I have already observed the sexual differences in the 
size of the canines and premolars of P. paliidosus and quite agree with Dr. Leidy 
in his interpretation of these facts, although in onr examples of P. paliidosus there 
is not a reduction in the complexity of the premolars with the increased size of the 
canine. This is certainly not the case, as in the female of P . paliidosus with 
smaller canines, the premolars are consideraldy smaller than in the male with its 
huge tusk-like canines. It is interesting to note that the superior premolar series of 
P. minor more closely resembles that of Telmatothcriiim and departs considerably from 
the characters of these teeth in P. paludosus. The first premolar has an elongated 
croAvn ; it is the exact connterpai't in form of this tooth in T. cultridens ; its para- 
cone is curved backAvards and compressed. There is only a verA^ slight indication 
of an internal cingulum to premolar 1, but the base has a slightl}^ enlarged heel. 
The first premolar is separated by a slight interval from the canine and the tooth 
sncceeding it. Premolar 2 has its anterior border very oblique AAuth its internal 
cone not strongly marked. Its external lobes are subeqnal, the paracone being con- 
siderably higher than the metacone. The anterior V of this premolar and those of 
all the succeeding ones ax-e pi’ovided Avith a pi’ominent median rib. Pi’emolars 3 and. 
4 have rather high croAvns AAntli equal external lobes. The latter are not separated 
by a median buttress. These teeth have traces of a protoconnle, although the 
latter lobule is in a A^ery rudimentary condition. The inteimal basal cingnlum of all 
the premolars is incomplete and the external cingulum of the third and fourth is well 
mai'ked. There is a difference in the ti’ans verse diameter of preniolar 4 and molar 
I in this species. The explanation offered by Prof Leidy of the difference between 
the two series of pi-emolai’s figui-ed by him is a very important one, and 
if his statement be cori’ect that in P. minor there is an increase in the com- 
plexity of the antei'ior pi-emolars Avith a decrease in the size of the canines, it 
obviates the necessity of making a neAV species out of a specimen, Avhich, in its 
true molar chai-actei’s, agrees almost exactly AAuth the typical example of this 
species. 
'Extinct Vertebrata, etc., page 36, 1873. 
44 JOUH. A. X. S. PHILA., VOL. IX. 
