224 Mr. H. W. Bates's Contributions 



Common to all three districts (seven being widely 



distributed neo-tropical species) .. .. 10 



Common to Upper and Lower Amazon only . . 4 



,, Lower Amazon and Para . . . . 5 



Peculiar to Upper Amazon .. .. .. 12 



„ Lower Amazon . . . . . . 2 



Para 8 



This result in an extent of country offering no great natural 

 barriers to Zoological distribution, situated within the same 

 parallels of latitude, and offering a great uniformity of mean 

 temperature (about 81° Fahr.), will be contrary to the precon- 

 ceived notions of most Zoologists on the subject. The whole 

 country, too, presents no diversity of elevation, so contrary to 

 other wide continental regions, and the rise from the Atlantic 

 towards the Andes is so slight, that at Tabatinga, 1,500 miles 

 from the mouth of the river, the height is only 650 feet above the 

 sea level. But, in fact, there are other minor climatal conditions 

 which operate, obscurely, but not less effectively, in influencing 

 the animal and vegetable population of a country ; and these it is 

 the proper business of a faunist to point out. In the first place, 

 the liigh lands of Guiana on the north, and of central Brazil 

 on the south, towards the middle part of the Lower Amazons, 

 approximate the banks of the river. They not only diminish the 

 breadth of the river valley and the extent of the alluvial low 

 lands, but they furnish from the detritus of tlieir own igneous 

 rocks a lighter and less prolific soil than that of the rich alluvial 

 plains of the Upper Amazon and Para. Through the soil the 

 vegetation is affected; the forests are not only less dense and 

 lower in height, but composed of a different class of trees. 

 Through the soil and the scanty nature of the forests the meteo- 

 rological forces are affected. The dry and the wet seasons are 

 far more strongly contrasted here tlian in the other parts of the 

 Amazon's course. Whilst at Para or at Ega there is never a long 

 uninterrupted dry season, rain falling more or less throughout ; 

 at Santarem and Villa Nova there is a season of always four, 

 sometimes six months, without a shower ; the dry woods become 

 parched, and the periodical phenomena in animal and vegetable 

 life present different features from those of the other two dis- 

 tricts. The hills which compose the two ranges of highlands 

 here alluded to are, however, of very small elevation ; they are 

 highest between Monte Alegre and Almeirim, below Santarem, 

 where they form a line of flat-topped ridges or truncated pyra- 

 mids, sometimes bare, sometimes wooded ; and with the mag- 



