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 l:)ehind the tooth in Hemigamts having 

 vanished in this later form. The tooth pattern of the molars is 

 like that of Heviiganus. 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 Ijasis other than 

 that established by such a method." It is not certain how many 

 toes upon the fore-limbs were possessed by Psittncotheriwii, but 

 the close resemblance to Mylodon is indeed striking, the third 

 digit being in 'both forms the most pronounced. Some vertebrae 

 of this G-anodont 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 pronoimced 

 among the Ungulata. The lower jaw has the same massive 

 structure that characterises that bone in He miganns and Psitta- 

 cotlierium. There is but one incisor, but the premolar and molar 

 series are complete. The canine is Eodent-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 tlie 

 form of vertical bands, leaving interspaces which are not covered 

 by enamel. These teeth, moreover, are decidedly hypselodont, 

 more decidedly so than in Psittacotherium ; they are, when unworn, 

 quadricuspidate, with accessory cusps ; when more worn, the teeth 



