448 Bulletin American Museum of Natural History. [A'ol. XXVII, 



AmhUjpoda. — In Coryphodon, as noted by Osborn (1889, p. 539) pari 

 passu with the increasing weight of the body and Avith the widening of the 

 distal end of the nhia, the carpus becomes very broad, the unciform grows 

 toward the inner side, overspreading the third metacarpal and broadening 

 the lunar-unciform contact; the magnum also spreads in the same direc- 

 tion, the lunar widens and causes the reduction of the scapho-centrale- 

 magnum contact. In Uiiitatherium these tendencies are carried to an 

 extreme (cf. p. 358). 



Hyracoidea. The carpal facets are more or less horizontal, so that the 

 proximal row articulates with the distal row by a horizontal and very con- 

 vex joint. The magnum is relatively large, the lunar partly overspreads 

 the trapezoid and centrale; the lunar-unciform contact is variable but it is 

 very evident in the back view at least in the specimens examined by the writer. 



Emln-ithopoda. The carpus is very similar to that of Elephas, while the 

 tarsus resembles the Corijphodon type. This may imply that Arsinoi- 

 therium has been derived from a short footed form with a carpus resembling 

 those of Meniscoiheriwn and Hi/ra.v and a tarsus like that of Pantolambda. 



Prohoscidea. The evolution of the manus in the Proboscidea has been 

 traced by Osborn (1889, p. 564, diagram 8) and by Weithofer (1890). In 

 correlation with the growth of the ulna and the reduction of the radius, the 

 cuneiform and especially the lunar, become very broad, the lunar over- 

 spreading the trapezoid and causing the reduction of the scaphoid. 



Pyrotheria. As shown by the casts in the American Museum of Natural 

 History, the manus ascribed to Pyrotherium is very Proboscidean in general 

 apj^earance, and differs from the manus of Masiodon chiefly in the extension 

 of the lunar over the unciform. According to Gaudry (1909) however the 

 reference of this manus to Pyrotlierium may be incorrect, and Gaudry 

 states that Tournouer has suggested that it pertains to Astrapotherium. 



In brief, the manus in the Condylarthra, Taligrada, Amblypoda, Hyra- 

 coidea, Embrithopoda, and Proboscidea is either progressively serial or at 

 least flattened. All exhibit a tendency for the carpals to change the oblique 

 into horizontal facets, so that the first row articulates with the second row 

 by more or less horizontal joints which extend across the carpus on about 

 the same level. The lunar is always broad and tends to spread inward 

 over the trapezoid, the scaphoid often loses contact with the magnum and 

 the scapho-centrale hook is reduced or absent. The lunar-unciform con- 

 tact usually becomes reduced (except in Taligrada and Amblypoda). 



Notoungidata. The carpal types of the Homalodotheria (p. 449), 

 Typotheria (]). 376), Toxodontia (p. 109), and Litopterna (p. 379) are very 

 diverse and include extreme interlocking types and })eculiar forms of the 

 serial type, but in no case do they show any features that seem inconsistent 



