CHAP. III.] 



ZOOLOGICAL REGIONS. 



49 



like starlings to the hang-nests, loteridos ; and these four 

 peculiar families comprise more than a hundred species, and 

 give a special character to the ornithology of the country. 

 Add to these such peculiar birds as the mocking thrushes 

 (Mimus), the blue jays (Cj^anocitta), the tanagers, the peculiar 

 genera of cuckoos (Coccygus and Crotophaga), the humming- 

 birds, the wild turkeys (Meleagris), and the turkey-buzzards 

 (Cathartes), and we see that if there is any doubt as to the 

 mammals of North America being sufficiently distinct to justify 

 the creation of a separate region, the evidence of the birds 

 would alone settle the question. 



The reptiles, and some others of the lower animals, add still 

 more to this weight of evidence. The true rattle-snakes 

 are highly characteristic, and among the lizards are several 

 genera of the peculiar American family the Iguanidse. No- 

 where in the world are the tailed batrachians so largely 

 developed as in this region, the Sirens and the Amphiumida;} 

 forming two peculiar families, while there are nine peculiar 

 genera of salamanders, and two others allied respectively to 

 the Proteus of Europe and the Sieboldia or giant salamander 

 of Japan. There are about twenty-nine peculiar genera of 

 fresh -water fishes ; while the fresh- water molluscs are more 

 numerous than in any other region, more than thirteen hundred 

 species and varieties having been described. 



Combining the evidence derived from all these classes of 

 animals, we find the Nearctic region to be exceedingly well 

 characterised, and to be amply distinct from the Palcearctic. 

 The few species that are common to the two are almost all 

 arctic, or, at least, northern types, and may be compared with 

 those desert forms which occupy the debatable ground between 

 the Palgearctic, Ethiopian, and Oriental regions. If, however, 

 we compare the number of species which are common to the 

 Nearctic and Palgearctic regions with the number common 

 to the western and eastern extremities of the latter region, 

 we shall find a wonderful difference between the two cases ; 

 and if we further call to mind the number of important groups 

 characteristic of the one region but absent from the other, w^e 

 shall be obliged to admit that the relation that undoubtedly 



E 



