177 
the Province of Buenos Ayrei 
$ . Upper mandible dark born-colour between the nos¬ 
trils, and from there to the corner of the mouth dull primrose- 
yellow. Under mandible, tip horn-colour, fading into prim¬ 
rose-yellow towards the base. Inside of mouth very pale 
horn-colour, with a tinge of yellow under the tongue. This 
species is common at JBaradero in April, but only black- 
plumaged birds are seen. 
39. Machetornis rixosa (Vieill .); Scl. et Salv. P. Z. S. 
1868, p. 143. 
Spring visitor, arriving in August ; but it does not seem to 
be a common bird. 
40. Centrites Niger (Bodd .); Scl. et Salv. P. Z. S. 1868, 
p. 142. 
Autumn and winter visitor, and common on open camp- 
land. Common at Baradero in April. 
41. Hapalocercus flaviventris (Lafr. et D'Orb.); Scl. et 
Salv. P.Z.S. 1869, p. 160. 
Having only observed this bird from October to April, I 
suppose it is a summer visitor. Between these months it is 
common in the riverain wood and in low damp places where 
the reeds afford any cover. Plentiful at Baradero in April. 
42. Serpophagasubcristata (Vieill.); Scl. et Salv. P. Z. S. 
1868, p. 142. 
Resident and abundant everywhere. Common at Baradero 
in April. 
43. Serpophaga nigricans (Vieill.) ; Scl. et Salv. P. Z. S. 
1868, p. 142. 
Resident, but not so common as the last-named species. 
I have always found this bird amongst the bushes and thick 
growth of sauce- and ceiba trees near the river. 
44. Cyanotis azar^i (Licht.); Scl. et Salv. P. Z. S. 1869, 
p. 159. 
Resident and common in reed-beds, generally found where 
there is a foot or so of water. It has a low piping note, which 
it constantly utters whilst busily hunting over the reeds for 
insects. Common at Baradero in April. 
