DIDELPHYID^. 287 



series is 0,011, and that of the true molars 0,006 ; the molars increase 

 in size posteriorly, and their talons are tricuspid. It is not easy to 

 see how this form ^ differs from D. laurillardi of the Paris gypsum, 

 or D. farva of Yaucluse ; in the latter of which the length of the 

 last three true molars is 0,005. 

 Bob. Europe (France). 



M. 2388 d. Fragment of the right ramus of the mandible ; from the 

 Phosphorites of Caylux (Tarn-et-Garonne), France. The 

 last three true molars remain, and have a united length of 

 0,005. Purchased, 1885. 



Didelphys aymardi (Filhol ^) . 



Syn. Peratherium aymardi, Filhol ^. 



About the size of D. antiqua. Lower molars increasing in size 

 from first to fourth ; pm. 1 very minute, separated by intervals from 

 canine and pm. 3 ', pm. 4 taller than pm. 3 ; talon of m. 4 tricuspid. 

 In the specimens described by Filhol * the length of the series of 

 lower cheek-teeth is 0,014, and that of the true molars 0,008 ; but 

 in the one figured by Gaudry in ' Les Enchainements, etc. — IVEamm. 

 Tert.' p. 11, fig. 1, these dimensions are rather larger. 



Sah. Europe (France). 



M. 2388. The nearly entire right ramus of the mandible, showing 

 all the teeth except the incisors ; from the Phosphorites of 

 Caylux (Tarn-et-Garonne), France. This specimen agrees 

 precisely with one figured by Gaudry, loc. cit. ; the length 

 of the space occupied by the seven cheek-teeth is 0,015, 

 and that by the true molars 0,009. Purchased, 1885. 



M. 2388 a. Hinder part of a similar right ramus, showing the last 

 three true molars ; from the same deposits. 



Purchased, 1885. 



Iff. 2388 b. Two rather smaller mandibular rami, in which the length 

 . of the four molars is 0,008 ; from the same deposits. 



Purchased, 1885. 



M. 1489-90. Two similar mandibular rami .; from the same deposits. 



Purchased, 1884. 



^ Owing to Gervais's error in regard to the dimensions of D. exilis, Filhol 

 compares the present species to that form. 



2 Bull. Soc. Philom. Paris, ser. 6, vol. x. p. 89 {ISl^).— Peratherium. 



^ Loc. cit. 



* Ann. Sci. Geol. vol. viii. art. 1, p. 251 (1877). The reference to the figure 

 is given as 388 instead of 387. 



