PAL.EOSYOPS LEIDY, AND ITS ALLIES. 
341 
this lobe may be rudimentaiy. The intermediate eonules of the premolars may be 
wanting, or, as in one of the species of this genus, they may be slightly develoj^ed 
on premolars 3 and 4. The true molars have their axes about ecpial, thus producing 
a square-shaped tooth ; this is especially noticeable in the last superior molar, whose 
internal border is square and not obliquely cut off as in the same tooth of Palcs- 
osyops. The crowns of the superior molars are very high as compared with 
those of PalcBosyops. The external V’s especially are broad, high and with sharp 
cutting lobes. The width between the buttresses of the external V’s is considerable 
in this genus, and the median buttress is strongly constricted olf. The anterior 
buttress is not so strongly developed as in Palcsosyops. The median valley between 
the external and internal lobes is very deep. The external cingula of the molars 
may be prominent. The two anterior molars are each provided with two internal 
cones, which are equal in height. In the last molar the protocone is always 
present, but the hypocong of this tooth is totally absent in one species, and in the 
other is merely represented bj^ a very small conule. The transverse diameters of 
premolar 4 and molar 1 are nearly equal, whereas in Palceosyops there is a marked 
difference in the transverse diameter of these two teeth. 
Lotver jaw. — The inferior incisors in this genus are more procumbently 
implanted in the alveolus than they are in P alceosyops and they are said to be more 
compressed and laniariform than in the latter genus. The lower canines are 
large, and a considerable post-canine diastema is present. The first lower premolar is 
slightly separated from the second, and it is more compressed and elongated than in 
P alceosyops. The crescents of the last two premolars are more strongly marked than 
in Palceosyops. The protoconid of premolar 1 is twice as high as its metaconid. 
In the last premolar the two V’s are more developed than in Palceosyops, and 
they approach more closely the complexity of the first true molar than they do in 
that genus. The true molars are provided with mucb higher crowns, and their 
antero-posterior diameter is much more extensive than in Palceosyops. The crests 
of the molars are also much higher, and their V’s much more strongly expressed than 
in Palceosyops. The posterior tubercle of the last lower molar in this genus is largely 
developed, its transverse diameter being nearly as great as that of the whole molar. 
This tubercle is more laterally placed than in Palceosyops and is provided with a 
well marked median valley and two lateral crests. 
Shill. — As far as known, the skull of this genus is narrower and much 
higher than that of the allied genus Palceosyops ; this applies especially to the facial 
region. The nasals are long and strongly arched laterally. The form of the premax- 
illaries is highly characteristic. They are strongly compressed, with a much 
elongated median symphysis, in this respect differing widely from the premaxil- 
laries of Palceosyops. As far as I have investigated, I have found no transition 
forms betAveen these tAvo genera as far as the shape of the premaxillaries is con- 
cerned. The palate is much elongated and strongly arched. The malar insertion 
is characteristic, being quite different from that of Palceosyops. The zygomatic arch 
