1884,] 547 [Cope. 
This genus is Leptauchenia without superior incisor teeth, and with but 
two on each side below. I originally asserted the presence of superior 
incisor teeth, and it is true that there is in early life a minute tooth in each 
premaxillary bone, as indicated by the alveoli in a specimen which con- 
tains the full deciduous molar dentition. I have not seen the teeth them- 
selves, and it is evident that they are early shed. In an adult specimen 
of 0. simus it seems that the alveolar portion of the premaxillary bone has 
been absorbed. 
The meatus auditorius externus occupies a more elevated position in 
this genus than in any other of the family. It is also directed somewhat 
posteriorly, There are postpariétal foramina, 
The cerebral hemispheres are not large, and scarcely rise above the 
plane of the summit of the large cerebellum. Yonvolutions three on each 
side, weakly defined. 
The concavity of the superior border of the premaxillary bones, to- 
gether with their upward production, leads me to suspect that the exter- 
nal nares were superior in position. This is the indication of an aquatic 
habit of life, such as is led by the hippopotamus. Like that animal, the 
nostrils in Cyclopidius were probably valvular to prevent the ingress of 
the water. The animals probably passed much of their time in the water, 
and the nostrils could be brought to the surface for the purpose of respira- 
tion, while the remainder of the head and body remained concealed, The 
prominent rim of the auditory meatus suggests a similar valvular closure 
of the organ of hearing, and is also a provision for its easy approximation 
to the surface of the water when necessary. 
The milk dentition is like that of Artiodactyla in general. That is, in 
the superior series the third molar is more elongate and complex than its 
permanent successor, and the fourth is like the first permanent true molar 
in constitution. In the inferior series the anterior three teeth resemble 
the permanent premolars, while the fourth is trilobate. 
In the loss of the incisor teeth and the subprismatic molars, we observe 
in Cyclopidius the same evidences of specialization already known in other 
types of Ungulates. 
I know of but two species of Cyclopidius. 
Cc 
rClopidius simius Cope. 
Proceedings American Philosophical Society, 1877, p. 221. Brachy 
merya feliceps Cope, Ibidem, p. 220 (immature). 
The specimens of this species in my possession embrace a complete 
skull with one zygoma and half of the brain-case wanting; a left maxil 
lary bone with all the tecth; and three mandibular rami with dentition, 
all of adults. Of immature individuals, I have two muzzles with denti 
tion of both sides, and six mandibular rami; in all, parts of thirteen in- 
dividuals. The following description of the skull is taken from the speci- 
men first named, which is the type of the species. 
The cranium is wide and depressed, and the muzzle is short. The pro- 
