330 
A MEMOIR UPON THE GENUS 
the hind brain in Pakeosyops distinguish this genus from recent Ungulates, approach- 
ing more nearly the conditions seen in the Condylarthra {Phenacodus) . 
Brain Measurements. ( Volume) . 
Taph'us iudicus 
Palceosyops megarhimis 
Hyrachyus eximius 
Ovis aries 
320 cc. 
180 “ 
096 “ 
095 “ 
Summary of Brain Characters.— following are the peculiarities of the 
brain of P. megarhinus -.—X. Reduced size of forebrain, especially the frontal lobes. 
2. Separation of fore-brain from hind-brain. 3. Large size of cerebellum. 4. Great 
breadth of the medulla oblongata. 
Brain Measurements of P. megarhinus. 
Total length of brain .... 
M. 
•100 
Length of hemispheres .... 
•070 
Breadth of hemispheres .... 
•Otl.5 
Height of hemispheres at temporal lobe 
.044 
Length of occipital lobe.s of hemispheres . 
•0.S4 
Lengtli. of frontal “ • 
•020 
Breadth of olfactory lobes .... 
•0:i8 
Breadth of mid-brain .... 
•037 
Breadth of cerebellum .... 
•05,5 
Antero-posterior extent of vermis 
•03(1 
Vertical height of eerebellnm 
■047 
Width of medulla ..... 
•04(1 
Pal.’eosyops minor. 
The relation of this smaller species of the genus Palceosyops to P. paludosus has 
been shown in our preliminaiy paper.' I will merely add that P. minor embraces 
specunens which Dr. Leidy erroneously assigned to P. paludosus. They are illus- 
trated by figures 3—6, Plate IV, of his report for 1873.“ They comprise a complete series 
of superior molars. Other specimens of this species figured by Leidy are a portion 
of the facial region containing the first three preniolars, and a finely preserved lower 
jaw which he represents on Plate V, figure 11. In the Princeton collection the 
material referable to this species is very limited. There is a partial set of molars. 
No. 10,242, and also three portions of jaws with the teeth rather damaged, speci- 
mens No. 10,042 a, b, c. I have alreadj^ mentioned the fact that the generic refer- 
ence of this species is uncertain. We know nothing of the anterior premaxillarv 
region of the skull, which is so important in distinguishing some of the genera of 
this subfamily. The characters of the teeth are very interesting, and show on 
the whole a more decided affinity to Telmatotherium than to Palceosyops although 
'Prelim. Obs. etc., Proc. Acad. Nat. Sci. Phila., Jan. 1891, page 112. 
"The type specimens of this species are in the Academy of Natural Sciences of Philadelphia. 
