350 UNGULATA. 



feet are typically tetradactyle, tlie lateral toes being well 

 developed ; but in .some forms {Diplopns) the second and 

 fifth digits are wanting, and the foot is two-toed. 



AVe have next a group of small Eocene and IMiocene 

 Mammals (the Xipliodontidce), which have affinities with the 

 preceding forms, and also with the following group of the 

 Anoplotherida: (especially to Dichohune and Dichodon) ; but 

 which likewise exhiliit relationshijjs with the Euminant 

 group of the Tragididcc (Chevrotains). The genus Xipliodon 

 itself comprises small Artiodactyle Mammals, with didactyle 

 feet, a short tail, and long and slender limbs. The dentition 

 is complete, the teeth forming a continuous series in both 

 jaws, and the canines being of small size. The molars (fig. 

 643, f) are of a generalised selenodont type, the lower 

 ones, having " two pairs of crescentic lobes with the convex- 

 ities turned outwards " (Owen). Cainothcrium includes small 

 Eocene and Miocene Mammals, also nearly allied to the 

 Tragvlidm, which resemble the preceding in most respects, 

 but have the lateral toes developed on all the feet. Micro- 

 therium, of the Miocene Tertiary of Europe, is also very near 

 to the true Chevrotains, but it differed from these, and agreed 

 with the preceding genera, in having a complete dentition, 

 the dental formula being — 



. 3—3 1—1 4—4 3—3 , , 



I ; c ; inn ; m = 44. 



3—3 1—1 4—4 3—3 



The upper molar teeth have three posterior cusps and two 

 anterior, as in Cainothcrium and Dicliobunc. The presence 

 of this additional posterior cusp in the upper molars is a 

 character shared also by the interesting Homacodon of the 

 Upper Eocene of Xorth America, which has a generalised 

 selenodont dentition, though in other respects allied to the 

 Suida. 



Fam. 3. Anoplotheridm. — We come next to the family of 

 the Anoplotheridce, which, in the present state of our know- 

 ledge, can with difficulty be limited precisely, or sharply 

 separated from some of the groups just noticed. The type 

 of this group is Anoplotherhim itself, of which there are two 

 or three species known from the Upper Eocene of Europe. 



