DIDELPHTID^. 283 



and that of the true molars 0,007 ; the mandibular ranms is more 

 slender, and the crowns of the molars are lower than in D. elegans. 

 Hob. Paraguay and South Brazil. 



18890 h. Three mandibular rami, probably belonging to this species. 

 The length of the cheek-series in the perfect specimen is 

 0,0105, and that of the true molars 0,0069. 



Didelphys, sp. a. 



Of still smaller size than the preceding, the length of the four 

 lower true molars being 0,006. 



18890 i. Six mandibular rami. 



OF UNCERTAIN SPECIES. 



18890 k. Five fragments of maxillae with teeth. 



B. EUROPEAN TERTIARY SPECIES.' 

 Didelphys affinis, Gervais \ 

 Syn. Peratherium affine, Gervais 2 . 



The length of the space occupied by the seven lower cheek-teeth 

 is 0,014, that by the last five cheek-teeth 0,010, and that by the 

 four true molars 0,007-75. The third and fourth premolars are 

 subequal ; the true molars increase in size from the first to the last, 

 and have bicuspid talons. Gervais doubts if this form is distinct 

 from D. cuvieri, Fischer 3 , of the Paris gypsum, but has given the 

 length of the lower cheek-series of the latter as 0,016, which appa- 

 rently comes nearer to D. antiqua. 



Hob. Europe (France). 



26792. Part of the left ramus of the mandible, containing the last 

 five cheek-teeth ; from the Upper Eocene (Lower Oli- 

 gocene) of Debruge, near Apt (Vaucluse), France. This 

 specimen apparently agrees precisely with the type man- 

 dible figured by Gervais in the ' Zool. et Pal. Franchises,' 

 pi. xlv. fig. 4. Pomel Collection. Purchased, 1851. 



Didelphys antiqua, Gervais *. 

 Syn. Peratherium antiquum, Gervais 5 . 



Closely allied to the preceding, but of rather larger size, the length 

 of the space occupied by the last five lower cheek-teeth being 0,012. 

 Hob. Europe (France). 



1 Zool. et Pal. Francises, 1st ed. vol. i. Exp. no. 45 (1848-52). 



2 Ibid. 2nd ed. p. 265 (1859). 



3 Synopsis Mammalium, p. 268 (1829). 



4 Zool. et Pal. Fransaises, 1st ed. Tol. i. Exp. no. 45 (1848-52). 

 s Ibid. 2nd ed. p. 266(1859). 



