SOUTH-AMERICAN MAMMALS. 227 



the dark spots on the naked part of the tail , as figured 

 in Alston's above mentioned book; in Tschudi's figure of 

 his D. ornata these spots are wanting. The descriptions 

 given by Tschudi and Wagner are sufficiently correct. The 

 skull nowhere has been figured or described. The figures of 

 the skull of our Samiria-specimen will discharge me of a 

 description. I now wish to compare it with skulls of other 

 Didelphys-s-peciea in our collection. All. the teeth are pre- 

 sent and it shows all characteristics of a fullgrown skull. 

 There is no sagittal crest like in skulls of adult specimens 

 of the other Didelphys-s^ecies of the same or of larger 

 size. The postorbital process of frontal bone is much more 

 developed than in any other Didelphyss-pecies at my dis- 

 posal , and in no species the skull is so short in proportion 

 to its broadness: the skulls of Didelphys philander figured 

 by Temminck in his »Mammalogie, T. I, pi. 6" are also 

 very short , they have been removed from young specimens 

 as the dentition indicates. The first premolar in upper and 

 lower jaw is very small. The second upper premolar is very 

 stout and much stronger than the third upper premolar, 

 the latter reaching about three quarter of the length of 

 the second upper premolar , meanwhile in the other Didel- 

 ^/«?/s-skulls the second and third upper premolars are about 

 of the same size or sometimes the third is higher than 

 the second. The second lower premolar attains about three 

 quarter of the size of the third lower molar and thus ap- 

 proaches more what I find in D. opossum , D. cancrivora 

 and D. azarae, although in these species in a lower de- 

 gree , meanwhile in the other species the second and third 

 lower premolar are nearly of the same size ; in D. tri- 

 striata the third lower premolar is somewhat higher than 

 the second. 



I think that a closer examination of larger series of 

 Didelphys-^^ViW^ than I have at my disposal, will bring us 

 to divide the Opossum-iamWy in some genera and to se- 

 parate D. lanigera in a peculiar genus, perhaps together 

 with D. philander: for the skull and dentition of D. la- 



Notes from tlie Leyden JMuseum , Vol IX. 



