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 1 differs from D. laurillardi of the Paris gypsum, 

 or D. parva of Vaucluse ; in the latter of which the length of the 

 last three true molars is 0,005. 

 Uab. 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 2 ). 



Syn. Peratlierium aymardi, Filhol 3 . 



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

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

 canine and pm. 3 ; pin. 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. Mamm. 

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



Hob. 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. 



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

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



PurcJiased, 1885. 



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



Purchased, 1884. 



1 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, se"r. 6, vol. x. p. 89 (1874).Peratherium. 



3 Loc. cit. 



4 Ann. Sci. G&il. vol. viii. art. 1, p. 251 (1877). The reference to the figure 

 is given as 388 instead of 387. 



