Cuap. VI. BIRDS AT OBYDOS. 131 
of sultry tropical days. In course of time the song of this humble 
thrush stirred up pleasing associations in my mind, in the same way as 
those of its more highly endowed sisters formerly did at home. There 
are several allied species in Brazil; in the southern provinces they are 
called Sabiahs. The Brazilians are not insensible to the charms of this 
their best songster, for I often heard some pretty verses in praise of the 
Sabiah, sung by young people to the accompaniment of the guitar 
I found several times the nest of the Carashué, which is built of dried 
grass and slender twigs, and lined with mud; the eggs are coloured and 
spotted like those of our blackbird, but they are considerably smaller. 
I was much pleased with a brilliant little red-headed manikin which I 
shot here (Pipra cornuta). There were three males seated on a low 
branch, and hopping slowly backwards and forwards, near to one 
another, as though engaged in a kind of dance. In the pleasant airy 
woods surrounding the sandy shores of the pool behind the town, the 
yellow-bellied Trogon (T. viridis) was very common. Its back is of a 
brilliant metallic-green colour, and the breast steel blue. The natives 
call it the Suruqua do Ygapd, or Trogon of the flooded lands, in 
contradistinction to the various red-breasted species, which are named 
Suruquds da terra firma. I often saw small companies of half a dozen 
individuals, quietly seated on the lower branches of trees. They 
remained almost motionless, for an hour or two at a time, simply 
moving their heads, on the watch for passing insects ; or, as seemed 
more generally to be the case, scanning the neighbouring trees for 
fruit; which they darted off now and then, at long intervals, to secure, 
returning always to the same perch. 
The species of mammals, birds, and insects found at Obydos are, to 
a great extent, the same as those inhabiting the well-explored tract of 
country lying along the seacoast of Guiana. No other locality visited 
in the Amazons region supplied, among its productions, so large a 
proportion of Guiana forms. The four monkeys already mentioned all 
recur at Cayenne. A general resemblance of the species to those of 
Guiana is one of the principal features in the zoology of the Amazons 
valley ; but in the low lands a great number exist only in the form of 
strongly modified local varieties ; indeed, many of them are so much 
transformed that they pass for distinct species; and so they really are 
according to the received definitions of species. In the somewhat drier 
district of Obydos, the forms are more constant to their Guiana types. 
We seem to obtain here a glimpse of the manufacture of new species in 
nature. The way in which these modifications occur merits a few 
remarks. I will therefore give an account of one very instructive case 
which presented itself in this neighbourhood. 
The case was furnished by certain kinds of handsome butterflies 
belonging to the genus Heliconius,* a group peculiar to Tropical 
* This genus has long been known under the name of Heliconia: a most incon- 
venient term, as a botanical genus bears the same name. An author has lately 
proposed to revert to the masculine termination of the words, as first employed by 
Linnzus (Felder, in the Wiener Entomologische Monatschrift, March 1862), and, 
as I think the correction a good one, I adopt it. 
