PAL.EOSYOPS LEIDY, AND ITS ALLIES. 
333 
Milk dentition^ (PI. XI I, tig. IG.) — There are two small teeth from the same 
individual, which I consider as probably belonging to the milk dentition. 
I have referred them to this species provisionally because they closely approach 
in form and general characters the molars of P. minor. The first tooth 
closely approximates in form to the superior premolar 2 of Telmatotheriutn. 
Its antero-posterior axis is much drawn out, the external lobes are very sharp 
and high, the internal face is provided with a prominent basal ridge, from 
which spring two rudimentary cones, the posterior being more plainly marked 
than the anterior. The anterior border of this molar is very obliquely cut 
off, and strongly reminds one of the form of tlie second superior premolar of Telma- 
tothei'iuni. The second tooth in this series is considerably larger than the first, but 
its general form is the same. The external V’s are more strongly expressed, the 
median buttress, being of the Tehnatotheroid type, is well constricted off. Both the 
external V’s of this molar are provided with well marked median ribs. The internal 
cones of the second molar are well developed and of the same size ; the protocoue is 
nearly separated from tlie internal cingulum, whereas tlie hypocone is still in its 
primitive condition and not separated. In both the above teeth tlie external 
cingulum is present, which shows their close relationship to Telmatotherium. 
The intermediate tidiercles of these molars are much reduced. A peculiarity of the 
external lobes of both these teeth is that they are very thin and much worn. The 
slightly worn V of the anterior tooth exhibits the abraded surface of the enamel 
much thinner than in the permanent dentition. Because of this character and their 
rather low crowns I have referred them to the milk dentition. There is one mandi- 
ble among the many in the collection which belongs to P. paliidosus. In 
this jaw the last milk molar is present, and, as is usually the case, is as comjilex in 
its structure as is the permanent first true molar. 
The Skull. — We are unfortunately entirely ignorant as to the form of the 
skull of P. minor, and, in fiict, I have seen only one specimen of a portion of the 
skull of this species, that figured by Dr. Leid}^ on Plate XXIV, fig. 6 of his work. 
I have unfortunately not been able to examine the facial region containing the 
molars above referred to, as it is in a private . collection. The specimen figured 
l)y Leidy' and the one which I have been able to examine contain the canine 
alveolus and the first three premolars. The form of this portion of the skull is 
high and narrow and resembles that of Telmatotliermm. The canine alveolus is 
peculiar in form : instead of being rounded as is usually the case, the surface of the 
muzzle above the canine forms an oblique ridge which runs parallel to the maxillo- 
premaxillary suture ; behind this ridge the surface of the maxillary bone is 
deeply hollowed out, and posteriorly becomes perfectly fiat. The form of the pos- 
tero-superior part of the premaxillary bone, which is preserved, leads me to con- 
clude that this region was more slender and elongated than in P. paludosus. The 
superior termination of the nasal process of the premaxillary was above the second 
'This specimen is now depo.sited in the collection of the Academy of Natural Sciences of Philadelphia. 
