ra 
1884, | 535 [Cope 
Measurements. M. 
Length of dental series (straight line)........... Pa rene a RO 
Sf from last molar to apex of coronoid............ 0785 
ss OT; PYSMOLT BORO vie eee wee nu wes teeceseees 000 
uy MUMS) MAGIAT SOMES ii ed's us 5/3 so dieia hate Cueva GcMnncE OCH 
sf ** second premolar on Dage. ....6..+ 00s Tae 021 
ve ‘TRY DRCMOLT ON DASE.) vee ere Seer ane eeo 
Depth of ramus at coronoid....... Resale ane eaten te rcareene hove OBOE 
" Pan CTCL Ne MDA Sie iai ilaly banana He Vaio OG 
WY SOC MOCO Lely cstv a sauiee mare oleh WOOO 
fy SO SE Li VOLVIGAII VAS vi chic ma hue e sv es 08: 
The specimens of this species were found by Mr. J. CO. Isaac in the 
Ticholeptus{beds of Deep river, Montana, during his Expedition of 1880. 
Merycochoerus rusticus Leidy. 
Report U. 8. Geological Survey Terrs., 1878, i, p. 199, Pl. III, figs. 1-3 ; 
VII, figs. 1-5 ; XX, figs, 9-81. Proceedings Academy Philadelphia, 1870, 
109. 
The smallest species, characterized among other things by the closure 
of that part of the nareal fissure which separates the premaxillary bones 
below. According to Leidy’s figure above quoted, the depth of the middle 
line of the undivided premaxillary is greater than the width of the bone, 
a state of things not approached by any of the species of this genus de- 
scribed in the preceding pages. The premaxillary in the JZ proprius is 
not described. 
From the ? Ticholeptus beds of the Sweetwater river, Wyoming. 
Merycochoerus proprius Leidy. 
Proceedings Academy Philadelphia, 1858, p. 24; Extinct Mammalia 
Dakota and Nebraska 1869, p. 110; Pl. X. 
This large species represents the extreme form of the genus in the ante- 
tior position of its dental series as compared with the braincase. The 
zygomatic arch and infraorbital foramen are therefore more posteriorly 
placed than in any other species. The premaxillary bone is more promi- 
nent than in any other, and the incisor teeth have relatively larger dimen- 
sions. The size is about that of the IZ superbus. Ihave not seen any 
other than the typical specimen. 
From the Ticholeptus beds at the head waters of the Niobrara river, 
Nebraska. 
MERYCHYWUS Leidy. 
Proceedings Academy Philad’a, 1858, p. 24, (nomen nudum), Extinct 
Mammalia Dakota and Nebraska, 1869, 115. Report U. 8. Geological 
Survey Terrs. i, 1878, p. 202. Cope, American Naturalist, 1884, p. 281, 
Ticholeptus Cope, Bulletin U. 8. Geolog. Survey Terrs., 1878, p. 380. 
Premaxillary bones coéssified ; otic bulla swollen; a vacuity between 
PROC. AMER. PHILOS. soc. xxi. 116. 8p. PRINTED JUNE 16, 1884. 
