2 5O The Naturalist in La Plata. 



patch, the throat thus having three strongly con- 

 trasted colours, arranged in four divisions. The 

 presence of this bright throat spot in so many 

 species cannot very well be attributed to voluntary 

 sexual selection, although believers in that theory 

 are of course at liberty to imagine that when en- 

 gaged in courtship, the male bird, or rather male 

 and female both, as both sexes possess the spot, 

 hold up their heads vertically to exhibit it. Per- 

 haps it would be safer to look on it as a mere 

 casual variation, which, like the exquisitely pencilled 

 feathers and delicate tints on the concealed sides 

 and under surfaces of the wings of many species 

 possessing outwardly an obscure protective colour- 

 ing, is neither injurious nor beneficial in any way, 

 either to the birds or to the theory. It is more 

 than probable, however, that in such small feeble- 

 winged, persecuted birds, this spot of colour would 

 prove highly dangerous on any conspicuous part of 

 the body. In some of the more vigorous, active 

 species, we can see a tendency towards a brighter 

 colouring on large, exposed surfaces. In Auto- 

 malus the tail is bright satiny rufous ; in Pseudo- 

 col aptes the entire under surface is rufous of a 

 peculiar vivid tint, verging on orange or red ; in 

 Magarornis the bosom is black, and beautifully 

 ornamented with small leaf-shaped spots of a 

 delicate straw-colour. There are several other 

 very pretty birds in this homely family ; but the 

 finest of all is Thripodectes flammulatus, the whole 

 body being tortoise-shell colour, the wings and tail 

 bright chesnut. The powerful tanager-like beak of 

 this species seems also to show that it has diverged 



