350 
A MEMOIR UPON THE GENUS 
mohr- from here anteriorly it widens, .and between the can.nes the jaw .a ttat 
Td t’rongly depressed. We see the beginning of tins e ongat.on of he jaw n, the 
lal er species of the genus; thus, in T. c«lM„s the diastemas anterior and ,.os- 
e or to premolar 1 have appeared, but they are not so strongly marked as In this 
snecies In P. paludosus on the other hand very much reduced diastemas appear 
to be the rule. In both examples of the j.aws of T. hyognalhus the menta foramina 
are double; the anterior being situated under the second premolar, while the i»s- 
terioris much smaller and placed between premolars 2 and 3. 
Comparative Measurements of Loiter Jaits. 
T. hyognathus. 
P. vallidens. 
Diplacodon. 
M. 
M. 
M. 
Distance from canine to dental foramen 
•350 
*•314 
Length of inferior molars, total .... 
•140 
•145 
•160’ 
r ant. post 
■063 
•057 
Last true molar -j 
•026 
•022 
Length of symphysis 
■122 
— — =' 
•180 
LIMNOHYOPS. 
(Syn. embraces Palxosijops as employed by Marsh, Limnohyus as employed by Loidy and others.) 
The type of this genus was descrihed by MarslU in 1872 under the name 
of Palceosyops laticeps. He also at th.at time described Ins Limnohyus robiistus. 
The former genus was characterized by haidug the last superior molar with 
two internal cones, and the latter by having this tooth with only one internal cone. 
Dr. Leidy,3 previously to Marsh, had fully characterized the genus IWwosyops, 
giving the characters of the teeth and skeleton quite fully, his description clearly 
showing that PalcBOsyops belongs to the Perissodactyles. Dr. Leidy, in his report 
for 1873, adopts Marsh’s name of Limnohyus for tho.se forms which have the last 
upper molar with two internal cones, but by the priority of Leidy ’s determination, 
both of the genera described by Prof. Marsh had liecome synonyms, and it was not 
until 1890 that the latter'* gave his two-coned type of molar the name Limnohyops. 
Dentition . — The characters of the teeth in Limnohyops are more closely I’olated 
to those of Paleeosyops than to those of Telmatothcrium, although the smaller species, 
L. fontinalis, has molar characters which, in some respects, |)oint to its aflinity with 
Tebnatotherium. The crowns of the molars in Limnohyops, like those of Palaosyops, 
are low and broad, with shallow valleys, the diameter of their transvei*se axes 
exceeding that of the antero-posterior. The external V’s of the molars are rounded 
* The measurements of P. vallidens are taken from Cope’s plate, the scale of which is incor- 
rect, and the above measurements are probably too large. 
’Estimated measurements. 
’’Am. Jour. Sci. and Arts, July, 1872. 
’’Hayden’s Prem. Kept. Geol. Surv. of Montana, etc., April, 1872. 
*Am. Jour. Sci. and Arts, June, 1890. 
