33O OREODON AND MESOREODON CHAP. 



Xiphodon was a hornless creature, but with only two toes, the 

 two lateral digits being represented by the merest rudiments of 

 rnetacarpals. The other metacarpals were unusually long. 



Amphimeryx (also called Xiphodontotlierimti) is much more 

 imperfectly known, but belongs to this family or to that of the 

 Caenotheriidae. Dichodon is another member of the same family. 



Fam. Oreodontidae. This family, consisting of numerous 

 genera, is limited to the North American continent. Its range 

 in time is from the Eocene to the Lower Pliocene. The family 

 as a whole is to be distinguished by a number of primitive 

 characters. The dentition is complete ; the feet are four- or 

 even five -toed ; the orbit is sometimes open behind. The canines 

 of the lower jaw are not more pronounced than the incisors. 

 The characteristics of the group will be further developed by 

 a consideration of some of the principal genera which are in- 

 cluded in this family. 



Oreodon is a Miocene form about as large as a Peccary. The 

 skull has a short face with a completely-closed orbital cavity. 

 In front of the orbit is a deep pit, not a mere deficiency of 

 ossification, such as occurs in many Artiodactyles. This is 

 placed on the lachrymal bone, and is in fact a lachrymal fossa, 

 such as occurs in other forms. The odontoid process of the axis 

 vertebra is somewhat cheese-taster shaped, as in recent Artio- 

 dactyles. There are fourteen dorsal vertebrae and a very large 

 number of caudals. The radius and the ulna are completely 

 separated, as are the carpals. There are five digits to the fore- 

 limbs. The fibula is complete and independent. The hind-foot 

 is four-toed. Several species of the genus are known. 



Merycochoerus is an allied Miocene genus. It is more 

 massive in form than the last, but otherwise does not present 

 differences of importance. 



Mesoreodon is another genus of this family which presents 

 some curious features of organisation. In the skull and teeth 

 there is nothing very noteworthy, but the hyoid is remarkable. 

 This appendage of the skull is by no means always preserved, 

 and when it is, it might be denied that it belonged to any 

 particular skull. In the present case there appears to be no doubt 

 as to the identity of the bones, which resemble the corresponding 

 bones of the Perissodactyla much more than they do those of 

 other Artiodactyles. Associated with the bones an ossified 



