THE OPOSSUMS. 219 
known. Length of head and body of male about 234 inches ; 
of tail 134 inch. 
Rio Grande do Sul. 
Distribution. 
XXI. THREE-STRIPED OPOSSUM. DIDELPHYS AMERICANA, 
Sorex americanus, P.L.S., Miller, Lin. Natursyst. Suppl., vol. 
Vii., p. 36 (1776). 
Sorex brazilensis, Erxleben, Syst. Regn. Anim., vol. i., p. 127 
(1777). 
Didelphys tristriata, Illiger, Abhandl. Akad. Berlin, 1811, p. 
107 (1815). 
Didelphys trilineata, Lund, Blik. Brasil. Dyrev., Dansk. 
Afhand., vol. viii., p. 237 (1841). 
_ Peramiys tristriata, Lesson, Nouv. Tabl. Régne Anim., Mamm., 
p. 187 (1842). 
_ Didelphys americana, Thomas, Cat Marsup. Brit. Mus., p. 363 
(1888). 
(Plate XX NV.) 
Characters—-This medium-sized and Shrew-like species is 
sufficiently distinguished from all the foregoing short-tailed 
_ Opossums by the presence of three dark longitudinal lines 
‘running down the back ; the general ground-colour being grey 
_or rufous. There are fifteen pairs of teats, of which five are 
central. Length of head and body of male about 54 inches ; 
of tail 22 inches; female rather smaller, with the tail rela- 
tively longer. 
Distribution. Brazil. 
Till the publication of the British Museum Catalogue of 
Marsupials in 1888, this species was almost universally known 
by the appropriate name of Didelphys tristriata, and since the 
_ object of nomenclature is to enable us to recognise and dis- 
tinguish animals with facility, it seems a pity that a rigid 
_ adherence to the rule of priority should have led to the substi- 
