On the Osteology of the Hyopotamldft^ 179 



to the same culminating point. In reaching it the lateral digits 

 \\ill be entirely lost, the trapezium will coalesce wdth the magnum, 

 and the second cuneiform with the third ; the middle metacarpals 

 and metatarsals will coalesce into a complete cannonbone; and 

 probably the stomach will become still more complicated, and they 

 will ruminate. That this state is the goal towards which the 

 Suina tend I have little doubt; but it is more than probable 

 that man by his influence \^ill prevent them from ever reaching 

 it. 



Our task is more difficult when we come to inquire into the line 

 of descent which has given rise to the E-uminantia. As stated 

 before, I cannot put the Anoplotherium, nor the Xiphodon, in their 

 pedigree. In my opinion, the line which ends in Euminantia 

 branched off from the small tetradactyle Hiiopotamidcp, which were 

 so numerous in the Eocene period. I find in the Eocene of Maure- 

 mont all stages of transition between the Jive-lobed dipper molars 

 of these Hyopotamidfe and teeth having a true ruminant four- 

 lobed pattern ; these last have belonged to some small species of 

 Dicliodon. Unfortunately we have no clue to the skeleton, though, 

 seeing the tetradactyle living Hi/omoschus, it may fairly be assumed 

 that these early progenitors of Euminantia were also tetradactyle. 

 The small tetradactyle Cainotherium is a very tempting genus in 

 specvdatious about the descent of Euminantia ; but I must exclude 

 it for many reasons, though I cannot here give them in f idl. Some 

 of these are as follows : — the Cainotherium retained till the Middle 

 Miocene five-lobed teeth on the Dichobune pattern (with the three 

 lobes on the posterior half of the tooth), while w-e have truly ru- 

 minant teeth already in the Eocene ; it retained its upper incisors 

 and free metatarsals, while the much older Gelams, Kym., which 

 is already a true ruminant, had no upper incisors and the meta- 

 podials were confluent in the adult. Cainotherium seems to be a 

 direct descendant of DicJwbune, and to have become extinct, w ithout 

 leaving any successors. 



Supposing that the Dichodon had a foot true to the tetradactyle 

 type, we do not find the earUest stages of reduction ; they were 

 passed rapidly, and in very ancient times : but there can be little 

 doubt that the Euminantia began with a tetradactyle foot, and 

 ended by a cannonbone adapted to the whole distal surface of the 

 carpus and tarsus. Such adaptation of the two middle digits could 

 not be obtained at one leap ; and certainly aU stages betw^een a 

 tetradactyle foot (in which every digit was supported by a separat<< 

 bone m the carpus and tarsus) and a didactyle foot (in w^hich 

 the two enlarged miodle digits have taken the whole distal surface 

 of all the carpal and tarsal bones) w^ere passed by this group in 

 the same manner as we have seen it in the Suina ; but onlv a few 

 traces of this passage remain. From the tetradactyle Dichodon, 

 the group of adaptive Selenodonts may be said to have split into 

 tW'O subordinate groups. In one of these, represented by the 

 Hyomoschus, the lateral digits are retained, and only the metatarsals 

 become confluent, while the two middle metacarpals continue to be 



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