350 Mr. H. W. Bates's Contributions 



remembered, that it is only the district of the north-eastern sea 

 board of the latter country and the river valleys near the coast that 

 are taken into consideration, that being the only part of the country 

 of which we have sufficient knowledge. Strictly speaking, the 

 northern shore of the Lower Amazons should be taken as part of 

 Guiana, forming, indeed, the southern frontier of the region j this 

 would reduce only, however, by one species the number peculiar 

 to the Amazon Valley. It is interesting to notice how the nmne- 

 rous local sub-species peculiar to Amazonia, all show themselves 

 to be local modifications of Guiana species; some of them (6) 

 being confined to the Upper Amazon, and others (2) to the Delta 

 at Para ; none of them being found on the northern or Guiana 

 shore of the Lower Amazon. It would thus appear that Guiana 

 is the great centre whence radiated the species which now people 

 the low lands on its borders, at their last emergence from the sea 

 or other waters ; and that some of them, in advancing westward 

 into the alluvial plains which occupy the wide basin of the Upper 

 Amazon, and eastward into the apparently recent land forming 

 the southern part of the Delta, have become modified into local 

 sub-species. The other great centres of distribution, Columbia 

 and Brazil, have sent but very few forms, in comparison, to 

 people these vast river valleys. The few Columbian forms found 

 on the Amazons (3 in number) occur only in the extreme west, 

 from Ega upwards. The Brazilian forms (2) occur on the south 

 shore, one indeed (Orsillus) does not reach the alluvial plains at 

 all, being found only in the narrow valleys of the hilly region of 

 the Tapajos, a southern affluent. A third form (Hierocles) might 

 be considered an Amazonian modification of a South Brazilian 

 species (^Proteus) ; this occurs only on the southern part of the 

 Delta at Para. The following table will show these facts in a 

 clearer light. 



Species peculiar to the Amazon Valley . . . . . . 8* 



Local sub-species ,, >» • • • • . . S-j- 



Species peculiar to Guiana with the Amazons . . . . 9 J 



,, „ Guiana alone .. .. . . 5§ 



Total number of species found in Guiana and Amazonia 50 



* Hierocles. Bolivar. Orellana, Aglaope. Echelus. Ergeteles. Columbus. 

 Chahrias. 



t Olivencius. Patros. Cyamon. Gayi. Cntora. hidorus. Paraensis. Parsodes. 



i Belus. Lycidas. Vertumnus. Mneas. ^neides. Lysander. Ariaralhes. 

 Triopas. Pausanias. 



§ Hippason. Eiiriiteus. Bitias. Arislaits. Pdiithoms. 



