1332 CLASS MAMMALIA. 



from the Quercy Phosphorites. The limb-bones, although all the 

 four digits are developed, show considerable resemblances to those of 

 the Ruminants, and it has been thought that Dichobunus may have 

 been the direct ancestor of Gelocus. Here also may be mentioned 

 the peculiar Upper Eocene European genus Acotherulum, in which 

 the general form of the skull and teeth of the one known species 

 seems to indicate affinity with Dichobunus, while the absence of the 

 third cusp on the hinder lobe of the upper true molars, and the more 

 completely bunodont structure of these teeth apparently indicates 

 affinity with Cebochcerus and its allies, among which some writers 

 prefer to place this genus. 



Family Dichodontid^e. — According to the views of Professor 

 Rutimeyer this family is taken to include several genera with a seleno- 

 dont dentition in which the upper true molars have four columns ; 

 the type genus Dichodon presenting affinities with Xiphodon, while 

 Gelocus and its allies are closely related to the Tragulidce and the 

 Cervidtz. Other writers, however, who do not attach such import- 

 ance to the structure of the molars, place Dichodon with Xiphodon 

 and make Gelocus the type of a distinct family. 1 In Dichodon the 



dental formula is I. ^, C. -, Pin. -, M. ± ; the upper true molars 



3 z 4 3 



having concave outer surfaces somewhat like those of Hyopotamus, 

 while the earlier premolars are elongated and secant, and thus ap- 

 proach those of Xiphodon ; there is no diastema. The limb-bones 

 are unknown, but it is probable that there were only two functional 



digits. This genus occurs in 

 the Upper Eocene of Hamp- 

 shire. In Lophiomeryx (fig. 

 1207) from the Upper Eocene 

 and Lower Miocene of the 

 Continent, the hinder inner 

 crescent of the upper true 



Fig. 1207.— The last four right upper cheek-teeth molars is imperfectly develop- 



pmJSE** Chalaniati; - from the Quercy ed, and the first lobe of the 



lower true molars resembles 

 that of Anoplotherium, while the second is Ruminant-like. The 

 lower molars also resemble those of Metriotherium (p. 1329), and 

 the family position of this genus, which is referred by Prof. Cope 

 to the Tragulidce, is still doubtful. L. Gaudryi from the Quercy 

 Phosphorites has been made the type of the genus Cryptomeryx. 

 In Gelocus, from the Quercy Phosphorites and Lower Miocene of 

 Puy-en-Velay, it is not known whether upper incisors were present ; 



1 Prof. Cope would include in this family the type genus and the American 

 Aeriochcerus and Coloreodon. 



