No. i.] OSTEOLOGY OF PCEBROTHERIUM. 43 



between the ento-cuneiform on the one side and the posterior 

 hook of the cuboid on the other. On the tibial side of mt. Ill 

 and the fibular side of mt. IV there are near the proximal end 

 small deep fossae for the rudimentary metatarsals. Mt. V is 

 never, in any specimen which I have seen, anchylosed with mt. 

 IV, and its contact with the cuboid is very small and almost 

 entirely lateral — a fact which we shall see to be not without 

 importance. The distal ends of the functional metatarsals are 

 broader than those of the metacarpals, but the carinas are not 

 more prominent, and are likewise entirely confined to the plantar 

 side. 



The pJialanges of the pes are in general like those of the 

 manus, but those of the proximal row appear to be decidedly 

 shorter (which is not sufficiently indicated in the restoration) in 

 the hind foot than in the fore foot. Kowalevsky has pointed out 

 the same difference in Anchitherium and the horse (No. 16, p. 65). 



The metapodials of PcebrotJierium, even the rudimentary ones, 

 are very similar in form and proportions to those of Xiphodon, 

 but with the important difference that in the latter genus the 

 reduction is an inadaptive one, while in the former it is adap- 

 tive. Schlosser, following Cope's description of the pes, has 

 regarded PcebrotJierium as inadaptively reduced (No. 27, p. 114); 

 but this is incorrect. In the manus, mc. Ill is in contact with 

 the trapezoid and has entirely excluded mc. II from the mag- 

 num, though the contact of mc. Ill with the unciform is still 

 considerable. In the pes, mt. Ill is supported solely by the 

 entocuneiform, the extension of mt. Ill taking up the whole 

 of the mesocuneiform, and excluding mt. II from it altogether: 

 the heads of Nos. Ill and IV are also on the same level, and 

 mt. Ill is no longer in connection with the cuboid. This is 

 "adaptive" reduction in its most typical form, and so far as the 

 Tylopoda are concerned, Kowalevsky's law holds good. 



VIII. Restoration (Fig. A). 



The abundant material now at command, and especially the 

 larger part of a skeleton belonging to a single individual, enables 

 us to give a restoration of this curious animal, in which there 

 would seem to be but little opportunity for error. PcebrotJie- 

 rium was a long-limbed, slender, and graceful animal with a 

 long neck and delicate, pointed head. In general appearance it 



