118 ZOOLOGICAL GEOGRAPHY. [PART m. 



may be claimed as exclusively Nearctic genera, on the ground 

 that Guatemala was recently Nearctic ; and is now really a 

 transition territory, of which the lowlands have been invaded and 

 taken exclusive possession of by a Neotropical fauna, while the 

 highlands are still (in part at least) occupied by Nearctic forms. 

 In his article on " Birds," in the new edition of the " Ency- 

 clopaedia Britannica " (now publishing), Professor Newton points 

 out, that the number of peculiar genera of Nearctic birds is 

 much less than in each of the various sub-divisions of the 

 Neotropical region ; and that the total number of genera is also 

 less, while the bulk of them are common either to the Neo- 

 tropical or Palsearctic regions. This is undoubtedly the case 

 if any fixed geographical boundary is taken ; and it would thus 

 seem that the " Nearctic " should, in birds, form a sub-region 

 only. But, if we define " Nearctic genera " as above indicated, 

 we find a considerable amount of speciality, as the following list 

 will show. The names not italicised are those which are repre- 

 sented in Mexico or Guatemala by peculiar species : 



LIST OF TYPICAL NEARCTIC GENERA OF LAND BIRDS. 



1. Oreoscoptes 17. Phcenopepla 33. Empidias 



2. Harporhynchus 18. Xanthocephalus 34. Sphyrapicus 



3. Sialia 19. Scolecophagus 35. Hylatomus 



4. Chamcea 20. Pipilo 36. Trochilus 



5. Catherpes 21. Junco 37. Atthis 



6. Salpinctjts 22. Melospiza 38. Ectopistes 



7. Psaltriparus 23. Spizella 39. Centrocercus 



8. Auriparus 24. Passerculus 40. Pedioccetes 



9. GymnokiUa 25. Pocscetes 41. Cupidonia 



10. Picicorvus 26. Ammodromus ? Ortyx 



11. Mniotilta. 27. Cyanospiza 42. Oreortyx 



12. Oporornis 28. Pyrrhuloxia 43. Lophortyx 



13. Icteria 29. Calamospiza 44. Callipepla 



14. Helmintherus 30. Chondestes 45. Cyrtonyx 



15. Helminthophaga 31. Centronyx 46. Meleagris 



16. Myiodioctes 32. Neocorys 47. Micrathene 



The above are all groups which are either wholly Nearctic or 

 typically so, but entering more or less into the debatable ground 

 of the Neotropical region; though none possess any peculiar 

 species in the ancient Neotropical land south of Nicaragua. But 

 we. have, besides these, a number of genera which we are accus- 



