866 



SCIENCE. 



[N. S. Vol. IV. No. 102. 



their tuberculate structure and all the 

 molars and premolars are more or less 

 elongated ; the incisors were reduced to a 

 single pair in the lower, and very probably 

 a like number in the upper jaw, with the 

 enamel confined to the anterior face. (3) 

 In the Wasatch representative {Ectoganus) 

 a still further advance is seen in that the 

 canines grew from persistent pulps; the 

 lower incisors had lost their enamel cover- 

 ing, and in the premolars the enamel is con- 

 fined to external and internal vertical bands. 

 (4) The Wind E.iver and Bridger genus 

 {Stylinodon) continues this specialization, 

 and here we note that in the premolars, and 

 miolars as well, the enamel is confined to 

 narrow external and internal vertical bands, 

 with all the teeth hypsodont and growing 

 from persistent pulps. (5) The feet of all 

 these genera, so far as known, are remarka- 

 bly short and provided with immense more 

 or less compressed claws. (6) The car- 

 pus and ulna and radius of Fsittacotherium 

 are almost identical with that of Mylodon, 

 and the humerus of Ectoganus displays a re- 

 markable similarity to that of Mylodon and 

 Megalonyx. (7) The muzzle 'is short, the 

 lower jaw is heavy and robust, and the pos- 

 terior end of the tooth line passes behind 

 the enlarged coronoid, which, together with 

 the large, powerful curved canines, grow- 

 ing from persistent pulps, at once recalls, 

 in the most positive manner, the skull of 

 Megalonyx. (8) The order Edentata, with 

 the exception of one or two fossil forms, 

 from the Santa Cruz and Monte Hermoso 

 beds of South America, are characterized 

 by enamelless teeth, growing from persist- 

 ent pulps, notwithstanding the fact, as has 

 been shown, that they possess a rudimen- 

 tary enamel organ for each tooth in the 

 earlier stages of its development. Ameg- 

 hino has found that some of the older 

 forms possessed bands of enamel on the 

 molars and premolars similar to those seen 

 in Stylinodon. 



We know of no other group of extinct 

 mammalia in which this progressive loss of 

 enamel occurs, coupled with increasing 

 length of the teeth, together with their 

 growth from persistent pulps ; and when we 

 come to consider the remarkable similarities 

 in other parts of the skeleton, the conclu- 

 sion, in my judgment, is unmistakable that 

 they are the direct forerunners of the Eden- 

 tata. It is, indeed, a matter of great surprise 

 that the foot structure of Psittacotherium, and 

 for that matter Hemiganus as well, should 

 show, even at the very beginning of the 

 Puerco, such a high degree of specializa- 

 tion, almost equal to the large Ground 

 Sloths. It clearly indicates that the modern 

 Edentates are the surviving members of a 

 very ancient and archaic group of mam- 

 malia, which had its origin far back in 

 Mesozoic time. 



It is also a matter of the greatest interest 

 to note that this group apparently disappear- 

 ed from ISTorth America before the close of 

 the Eocene, no trace of them having as yet 

 been found later than the Lower Bridger 

 horizon, until they reappear in the Pliocene 

 or Post- Pliocene beds of this country. It 

 is also worthy of note that they make their 

 first appearance in South America in the 

 Santa Cruz and Monte Hermoso formations, 

 which would seem to indicate that these 

 beds cannot be older than late Eocene or 

 older Miocene, corresponding with our 

 Uinta and White River formations. Col- 

 lateral evidence of this migration to the 

 southward in Eocene time is furnished by 

 the disappearance of Meniscotherium from 

 our Wasatch and the subsequent appear- 

 ance of its successors, the Proterotheriidce in 

 South America. 



I think, from the evidence just adduced, 

 that it can now be established that the 

 South American Edentata, at least, origin- 

 ated on the North American continent in 

 the group above described. 



J. L. WOKTMAN. 



