604 Mr. O. Thomas on 



Metachirus opossum azaricus, subsp. n, 



A uniform grey subspecies witliout blackened crown. 

 Size rather smaller than in other subspecies. General 

 colour above uniform mouse-grey without median dorsal 

 darker line, the sides scarcely ligliter than the back. Under 

 surface buify throughout, of greater or lesser intensity. 

 Ciown only faintly darker than the back, not definitely 

 blackened as it is in most of the allied forms. Eyes, how- 

 ever, surrounded by black as usual. Supraocular spots 

 fairly large, but not very sharply defined ; their diameter 

 about 12 mm._, the space between them too vaguely defined 

 for exact measurement, but somewhere about 9 mm. broad. 

 Aims and legs grey, paler than the body. Hands and feet 

 dull whitish. Tail with about half the scaly portion white. 

 Dimensions of the type (measured in the flesh) : — 

 Head and body 277 mm. ; tail 295 ; hind foot 35 ; ear 36. 

 Skull : condylo-basal length 65 ; ms^~^ 10'2. 

 Ilab. Paraguay. Type from Sapucay. 

 l^pe. Old female. B.M. no. 3. 2. 3. 36. Original 

 number 820. Collected 8th August, 1892, by W. Foster. 

 Eight specimens. 



By its smaller size and unblackened crown this Opossum 

 is readily distinguished from the other subspecies of 

 M. opossum^ although the black crown is not always very 

 strongly developed in the Brazilian AI. o. qidca. 



1 cannot refrain from naming it in honour of the famous 

 Paraguayan naturalist Azara, as the animal I previously 

 named after him, Pseudalopex azarica^ suffered a nomencla- 

 tural mishap, as was also the case with the well-known 

 DideljMs azarce, whose name proved to be antedated by the 

 ugly term D. paragayensis^ Oken. 



Another name of Oken's, Didelphis austro-americana^ ^ 

 belonging to the present group, should be considered as a 

 synonym of D. opossum, L., as its basis is the same as that 

 of opossum^ and, now that the latter name has been restricted 

 to the Surinam animal, austro-americana should follow it as 

 a synonym, leaving quica available for the Brazilian sub- 

 species. 



Metachirus opossum crucialis, subsp. n. 



A pale grey form without median dorsal line. 

 General colour ])ale mouse-grey, though the type may be 

 a little faded. Median area of back not darker, so that the 



* Lehrh. Nat. iii., Zool. ii. p. 1148 (181(3). 



