BARBOUR AND NOBLE: LIZARDS OF THE GENUS AMEIVA. 423 



Although no very satisfactory conclusions, perhaps, can be reached 

 regarding the main question of the origin of the species of this genus, 

 nevertheless one feature stands out strongly and clearly, and this is 

 that the distribution of the Antillean species show by their relationship 

 to one another and to the mainland types that they arose from an 

 orderly progressive migration, such as would only be possible over a 

 continuous area of land, and in no wise display the haphazard char- 

 acter which would be the only possible character of a flotsam and 

 jetsam fauna. When we remember that the Ameivas of twenty-six 

 different islands are already known, this conclusion will in no wise 

 surprise those naturalists who know these creatures in their native 

 haunts. Quick and active, absolutely terrestrial, they are farthest 

 removed in habits from the lizards which we now know are at times 

 moved about fortuitously, probably most often by human agency. 

 The gekkos which hide in or under the bark of trees, enter and abide 

 in human habitations, were from the nature of their secretive ways 

 probably a frequent companion of primitive man while upon his 

 journeyings. The skinks seem also, probably largely on account of 

 their very small size, to have been spread far and wide, especially 

 in the Pacific Island area, by human agency, and with these resistent 

 creatures dispersal by fortuitous flotation probably occurs, but we 

 cannot believe that it ever takes place except under the rarest and 

 most exceptional cases with even these skinks. With other types, so 

 many of which could never be imagined, starting on, surviving, or 

 landing from an ocean voyage taken upon a sodden, water-soaked 

 natural raft, it is quite useless to argue that the enormous length of 

 geologic time makes it possible to say that such flotation may occasion- 

 ally occur even using occasionally in a geologic time sense. That so 

 many, many types would die invariably were they started forth 

 annually or monthly upon a rafting voyage, makes but the more 



Explanation of the Diagram. 



The diagram, page 422, shows the relationship of the different species in the 

 genus, the name of each race standing with relation to the others in geographic 

 position. Each name occupies a position as near as possible identical with the 

 area its habitat would occupy if the whole diagram were superposed upon a 

 map of the Antillean region, Central America, and South America, the latter 

 somewhat contracted. 



