Vill PSITTACOTHERIUM IOI 
logical order. The following genera are included by Wortman in 
his family Stylinodontidae. 
The earliest type of the Ganodonta is the genus Hemiganus, 
with but one species, H. ofariidens. This animal lived during 
the deposition of the lowest Eocene strata, the Puerco beds of 
North America. It was about as big as a fair-sized Dog, and had 
powerful jaws. There were at least two pairs of incisors in the 
upper jaw, together with powerful canines and the full premolar 
and molar formula. In the lower jaw the canines were also 
strong, but the incisors are not certainly known to be more than 
two pairs. The enamel upon the posterior surface of the canine 
is thin, and in the case of the incisors the enamel seems to be 
limited to the anterior face. The lower molars are quadrituber- 
cular. It is believed from the presence of a suture on the upper 
surface of the premaxillary that the snout of the creature was 
tubular. The cervical vertebrae, only known by their centra, are 
like those of the Armadillos (and for the matter of that of the 
Whales) in the great transverse as opposed to the antero-posterior 
diameter. The feet are especially compared with those of the 
Ground Sloths. The single ungual phalanx is marked by a large 
subungual process, which is pierced by a considerable foramen. 
The tibia again is to be compared with that of the Armadillos. 
In the Upper Puerco (Torrejon) beds the remains of Psitta- 
cotherium are found. This genus, when first discovered, was 
referred to the Tillodontia by some and to the Ungulates, the 
latter being a refuge for indeterminate Kocene mammals, just as 
the “ Multituberculata ” is for similarly-placed Secondary mammals. 
It is now known to be clearly a member of the order Ganodonta. 
Wortman thinks that there is but one species, P. multifragum. 
It seems to have had a general aspect much lke that of Hemz- 
ganus—that is judging from the skull—and was not very greatly 
different in size. The facial portion of the skull is short, and the 
zygoma is deep. The infra-orbital canal is double, a feature which 
crops up in the Sloth, and has been mentioned in the later form ot 
Ground Sloth, Megalonyx (but it must be remembered that the 
same characteristic is not unknown in Rodents). The dentition 
is reduced as compared with that of Hemiganus, that is to say, as 
far as concerns the molars and the incisors. There is but a single 
pair of incisors in each jaw; the canines are strong; the premolar 
and molar series seem to have been complete in the lower jaw, 
