DICHODONTID^J. 159 



occupied by the three true molars is 0,033, and the depth 

 of the ramus in front of m . 1 0,0156, and behind m. 3 

 0,027. Purchased, 1884. 



Family DICHODONTID^E. 



In the type genus the full complement of the typical Eutherian 

 dentition is developed ; but it is not yet known whether the upper 

 incisors were present in some of the other genera. The cheek- 

 dentition is selenodont, the upper true molars being quadricolumnar ; 

 but in Lophiomerycc some of the columns are imperfectly developed. 

 The family appears so closely connected with the Tragulidce, that it 

 is dim cult to draw any distinctive division, unless it be eventually 

 found that upper incisors are always present. The foot-structure 

 in those forms in which it is known presents considerable specializa- 

 tion. Choeromeryx, which is provisionally included in the family, 

 appears to indicate affinity with Merycopotamus pusillus. 



Genus GELOCUS, Aymard \ 



The upper molars of this genus have extremely low columns with 

 wide open valleys ; the external surface of the hinder lobe of each 

 of the outer columns is markedly concave, indicating affinity to 

 Dichodon. The navicular and cuboid bones of the tarsus are united ; 

 and the hinder metapodials fused into a cannon-bone. The dental 

 formula is I. |, C. \, Pm. | M. |. 



Gelocus communis, Aymard 2 . 



Syn. Anthracotlierium minutum, Blainville 3 . 



Amphitraguhis communis, Aymard *. 

 Hah. France. 



27596. Fragment of the left ramus of the mandible, containiug the 

 last two premolars and the three true molars ; from the 

 Lower Miocene of Eonzon, near Puy-en-Yelay (Haute 

 Loire), France. The space occupied by the three true 

 molars measures 0,024 ; which agrees with typical speci- 

 mens. Croizet Collection. Purchased, 1848. 



1 Ann. Soc. Agric. Sci. Le Puy, 1855 (teste P. Gervais). 

 - Ibid. vol. xii. p. 247 (1848), Amphitragtdus {teste Filhol). 



3 ' Osteographie,' Genus Anoplotherium, p. 132 (1846). This specific name 

 has the priority, but as it is not applicable when transferred to Gelocus it has 

 been dropped. 



4 Loc. cit. 



