240 MR. H.W. BATES ON BUTTERFLIES FROM PANAMA. [JuilC 23, 



Thus, if we withdraw those species, twelve in number, which (being 

 foujid in open situations, generally in the suburbs of towns, and pos- 

 sessing large powers of dissemination) are widely distributed in Tro- 

 pical America, an analysis of the collection yields the following re- 

 sults : — 



Species not found in the Guiano-Amazonian region (six of 

 which are new) 1 .5 



Species found in the Guiano-Amazonian region, but not 

 extending their range further southward 4 



Of the twelve generally distributed neotropical species, four present 

 themselves in the form of tolerably well-marked varieties which seem 

 to be peculiar to Panama and Central America. It may also be 

 added that one of the four species which extend to the Guiano-Ama- 

 zonian region reaches no further than the western part of the Ama- 

 zons plains. The six new species contained in the collection are all 

 more or less nearly related to New Granadian and Guianian forms, 

 except one (Papilio xanticles), the nearest relative of this Papilio, 

 from which, however, it is well distinct, being a Mexican species. 



It may perhaps be premature to draw any inferences from these 

 data bearing upon the former physical condition and changes of these 

 regions, seeing that a much more extensive basis of facts is required, 

 which can only be obtained by an analysis of the whole Columbian 

 fauna ; but it may be useful to point some of them out as an incite- 

 ment to further research. For instance, as a large amount of pecu- 

 liarity in the existing fauna of any land-area must prove that its 

 inhabitants have not, geologically speaking, recently migrated to it, 

 such area must be the site of a land of high geological antiquity. 

 Moreover, as the productions which furnish these data are species 

 belonging to genera and groups which inhabit only the low, warm, 

 and humid forests of Tropical America, this ancient land must have 

 always possessed districts supplying these same physical conditions. 

 It cannot at present be decided how far this land extended to the 

 south, as our knowledge of the productions of Eastern and Central 

 Peru and Bolivia is at present very limited ; but towards the north, 

 the considerable change of species seen in Southern Mexico, which 

 possesses districts very similar in physical conditions to many in Co- 

 lumbia, would seem to show that there was formerly a separation 

 between the two regions, in the same way as the great dissimilarity 

 between the faunas of Columbia and Guiana would show this to have 

 been the case between these two now continuous lands. This latter 

 conclusion, however, must be drawn with great caution, as a diversity 

 of fauna between adjoining areas, even although their physical condi- 

 tions may appear to us almost identical, does not necessarily prove 

 the existence of a former physical barrier between them ; for I found 

 in the alluvial forest-plains of the Amazons that different small areas 

 continuous with each other contained each their separate represen- 

 tative species, proving that some other cause besides physical barriers 

 operates to limit the ranges of species. 



