THE STRUCTURE AND RELATIONSHIPS OF ANCODUS. 493 
in the other two genera, both having the spine placed in the middle of the blade, 
dividing It into subequal fossae. In some species of Ancodzis the blade is broader 
in proportion to its height than in Oreodon, while in others the resemblance in out- 
line IS exact, and in all the similarity is much greater to the latter genus than to 
Anoplothermm. The character and position of the acromion are also alike in the 
two genera. 
' The humerus is much alike in Ancodus and Oreodon. In the former the inter- 
condy lar ridge of the distal trochlea is narrow and compressed, while in the former 
it is broad and hemispherical, and in both the internal epicoiidyle is very conspicu- 
ous. In AgriocJmrus the distal portion of the humerus has its oreodont peculi- 
arities so exaggerated as to closely approximate the creodont structure ; this is to 
be seen in the breadth and lowness of the trochlea, perforation of the supra- 
trochlear fossa, and the great prominence of the inner cpicondyle. In this way the 
resemblance to the humerus of Mesonyx is made remarkably close ; indeed the 
humerus of the latter is more ungulate in appearance than is that of Agriochcerus. 
The radius and ulna are much alike in all three lines; the former has a slender, 
subcylindrical shaft, which is most widened and flattened in Ancodus, while the 
distal end in Agriochcxrus has become very creodont-like. The ulna is very little, 
or not at all reduced, and has a very large olecranon, which in 07 'eodon is very 
high, and in Ancodus (juite low. 
The carpus, again, displays in each of the three lines certain specializations 
peculi.'ir to each, but with a general similarity throughout; in Agriochoertis we find 
the widest departure from the common plan. In the oreodonts there is a strong 
tendency in the magnum to shift altogether beneath the scaphoid and to retain 
only a lateral contact with the lunar. This tendency, which is plainly incipimit m 
Protoreodon, reaches its maximum in Merycochoertis and Merychyus.^ A similar 
tendenev, though very much less marked, is observable in Ancodus, while in Agno- 
c/icerus the displacement is in the opposite sense, the magnum shifting toward the 
ulnar side of the hand. The individual carpal elements are quite alike in Ancodus 
and Oreodon, and in all three genera the trapezium is present and of some func- 
tional im}K)rtance. i- i i j 
The manus is pentadactyl in all three lines, except in some of the later and 
larger specimens of Agriochoerns, which seem to have lost the pollex. _ The first 
digit iB rehatively best developed in Ancod,is. In all three the connections of 
metacarpus will, the carpus are of the unreduced type, the third metacarpal being 
excluded from the trapezoid by the contact of the second w.th the magnum In 
Oreodon and Ancodus the phalanges are similar; the nng.mis are very char er- 
istic and of a type not common among the artiodacty s. The European spec, es of 
.. , n I fide fvne of ungual, giving a smaller and more 
Ancodus seem to have modilied tins type ^ ^ 
pointed hoof than in the American foims. ^ 11^ TLfv nno-iials are 
LtiodaetyU, recent or extinct, in the character of tts “J" ^ 
large, eon.pmssed, and claw-like, and the art.culat.ons »f 
semble those of the A,uylopoda rather more thau those of the ungulates. 
