192 GANODONTA—CALAMODON CHAP. 
but reduced by one premolar at least in the upper jaw. It is very 
important to notice that the incisors have enamel only on their 
anterior faces, and that the same is the case with the canines, 
the slender layer present behind the tooth in Hemiganus having 
vanished in this later form. The tooth pattern of the molars is 
hike that of Hemiganus. The fore-limb is decidedly Edentate- 
like; but it is the foot which presents the strongest likenesses to 
that order. “If an anatomist,’ remarks Dr. Wortman, “had no 
other part of the skeleton than that of the foot to guide his judg- 
ment, and he should fail to detect a most striking similarity 
between it and that of the Edentata, especially the Ground Sloths, 
he would not only lay himself open to the criticism of being 
lacking in the ordinary powers of observation and comparison, but 
would be suspected of placing the matter upon a basis other than 
that established by such a method.” It is not certain how many 
toes upon the fore-lmbs were possessed by Psittacotherium, but 
the close resemblance to Mylodon is indeed striking, the third 
digit being in both forms the most pronounced. Some vertebrae 
of this Ganodont have been discovered which do not show the 
complex articular arrangements of later American Edentates. The 
sacrum, on the other hand, is very like that of the Sloth, and there 
is a foreshadowing of the attachment of the ilia to the sacrum by 
co-ossification which is met with in later Edentates. A still later 
type is the genus Calamodon, which has been shown to occur in 
Europe as well as in America. C. simplex was a larger beast 
than either of the genera that have already been treated of, thus 
affording another example of the increase in size of later as com- 
pared with earlier members of the same group, so pronounced 
among the Ungulata. The lower jaw has the same massive 
structure that characterises that bone in Hemiganus and Psitta- 
cotherium. ‘There is but one incisor, but the premolar and molar 
series are complete. The canine is Reodent-like in appearance, 
being imbedded throughout the greater part of the lower jaw ; it 
evidently grew from a persistent pulp. It is enamelled upon the 
anterior face only. The premolar and molar teeth are in this 
genus commencing to lose their enamel, which is distributed in the 
form of vertical bands, leaving interspaces which are not covered 
by enamel. These teeth, moreover, are decidedly hypselodont, 
more decidedly so than in Psittacothervwm ; they are, when unworn, 
quadricuspidate, with accessory cusps; when more worn, the teeth 
