A MEMOIR UPON THE GENUS 
34G ^ 
f thPv are flat and wider than at their anterior portion. The extremity 
rf tt"na;als 1 'not expanded. The inferior border of the nasal notch is well 
l^ved in this skull and shows it to be nearly honzontal m positron and more 
etagate than the skull of P. pMosus. The snpenor term.nat.on of the nasal 
notch is above the second premolar. + i i 
Maxillary.-^\^^ vertical plate of the maxdlary m mnch elongated and 
hiMi above the malar region. The infraorbital foramen is large, iflaced above the 
anterior border of the first true molar and is more exposed Rian rn P paludosus. 
The form of the alveolar border of the maxillary is very different in Hus species 
from that of the larger species of Palaosyops. In T. cultr^dens border is 
stroiiMy convex and the anterior portion bearing the canine is much higher than the 
posterii alveolar region, thus making the anterior facial region rise strongly above 
the malar insertion. The horizontal lamina of the maxillary, forming a part of the 
palate is much larger and narrower than in P. paludosus, the narrowness being 
especially noticeable in the premaxillary region. The inferior surface of the 
palate is strongly arched ; this is especially marked when the facial region is 
viewed from the front. The superciliary border of the orbit is much more elon- 
gated and higher than in PalcBOsyops ; the floor is very broad and long, and its 
transverse and longitudinal diameters are nearly twice as great as those of P. 
paludostis. 
Malar.— T\\e malar insertion is peculiar in T. cultridens. It arises abruptly 
from the cheek with an anterior rounded border ; its external face is provided with 
a blunt keel separating the bevelled superior surface from the iiarnnv and sharp 
inferior portion. The orbital process of the malar is not well marked in tliis skull, 
but the superior process from the frontal bordering the orbit posteriorly is large and 
not acuminate. The temporal ridge arising from the latter is not so obli<iue in its 
course as in P. paludosus, indicating that these ridges were farther apart than in 
that species, the forehead consequently being flatter. The portion of the malar pos- 
terior to the orbit is very small and oval in section. The anterior part of the 
zygomatic process of the squamosal is preserved, and shows this portion of 
the arch to have been straighter and narrower than in P. paludosus ; its external 
face is flat and its posterior portion narrow in form as in P. mcgarhiuHS. The 
zygomatic arch, as a whole, in P. cultridens is much lighter and more horizontal in posi- 
tion, and it does not project so widely' from the skull as in P. paludosus. It is inter- 
esting to note that the zygomatic arch of Diplacodon elatiis is slender and straight, 
and much more closely resembles that of Telmatotherium than that of Palceosyops. 
This supports the view that Telniatotherhwi and not Palceosyops is the 
immediate ancestor of Diplacodon. 
Mandible. — The mandible is longer and straighter than that of P. palu- 
dosus. This applies particulaidy to the lower border of the jaw, which is per- 
fectly straight from below the last true molar to the anterior premolar region, 
the portion of the jaw in front of the latter region being arched upward and forming 
