42 SCOTT. [Vol. V. 



inence as in the llama. The distal surface displays two facets, 

 — a large and nearly plane anterior one for the coalesced ecto- 

 and meso-cuneiforms, and behind this a small and somewhat 

 concave one for the ento-cuneiform. 



Cope has incorrectly stated that the ento-cuneiform was 

 missing, and that the ecto-cuneiform alone supported the third 

 digit (No. 8, p. 487). As a matter of fact, the third digit is 

 supported by a compound bone, composed of the coalesced ecto- 

 and meso-cuneiforms, while the ento-cuneiform is also present. 

 The latter is the smallest of the tarsal bones ; it is wedged in 

 between the navicular and the rudimentary second metatarsal, 

 and behind is in contact with the stout posterior hook of meta- 

 tarsal III, but does not touch the latter in front. The com- 

 pound cuneiform is relatively higher and narrower than in the 

 recent genera : it has no contact with mt. II. Except for 

 differences of proportion and a few variations in details, the 

 tarsus of the Tylopoda had already attained in PcebrotJierium 

 to substantially the same condition which it still retains. 



The metatarsus (PI. Ill, Figs. 50, 51), like the metacarpus, 

 consists of two functional digits, the third and fourth, and of 

 two reduced, scale-like rudiments, the second and fifth. Mt. 

 II has an enlarged head with an oblique facet, directed down- 

 ward and backward, which articulates with the ento-cuneiform ; 

 it is entirely excluded from any contact with the meso-cunei- 

 form by the extension of mt. Ill over that bone. In some 

 specimens mt. II is free, while in others it is firmly co-ossified 

 with mt. Ill, though its limits are always plainly visible ; it 

 is considerably longer than the corresponding metacarpal, but 

 is nevertheless short, and rapidly tapers to a point. 



Mt. Ill and IV are much longer than the metacarpals, while 

 in the recent genera the fore and hind cannon-bones are of 

 almost the same length. In Pcebrotlierium the length of the 

 metacarpus is 85, that of the metatarsus 95 (that of the humerus 

 being 100) ; in Camelus these proportions become 93 and 97, in 

 Aucliciiia 101 and 99; so that the Miocene genus has nearly 

 attained the modern standard so far as the length of the meta- 

 tarsus is concerned. Mt. Ill is considerably stouter than its 

 fellow, to which it is very closely applied, and the two were 

 held together by the manner in which the long hook-like pro- 

 cesses from the plantar side of the proximal ends are wedged in 



