ZOOLOGICAL GEOGRAPHY. 



[PART III. 



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 Pahearctic 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 



2. Harporhynchus 



3. Sialia 



4. Chanma 



5. Cathcrpes 



6. Salpinctus 



7. Psaltriparus 



8. Aurijmrus 



9. Gymnokitta 



10. Picicorvus 



11. Mniotilta. 



12. Oporornis 



13. Icteria 



14. Helminthcrus 



15. Helmirdhophaga 



16. Myiodioctes 



17. Pluenop>epla 



18. Xanthocephalus 



19. Scolecophagus 



20. Pipilo 



21. Junco 



22. Melospiza 



23. Spizella 



24. Passerculus 



25. Pocecetes 



26. Ammodromus 



27. Cyanos])i~a 



28. Pyrrhuloxia 



29. Calamospiza 



30. Chondestes 



31. Gentronyx 



32. Neocorys 



33. Empidias 



34. Sphyrapicus 



35. Hylatomus 



36. Trochilus 



37. Atthis 



38. Ectopistes 



39. Centrocercus 



40. Pedioccetes 



41. Cupidonia 

 1 Ortyx 



42. Oreortyx 



43. Lophoi-tyx 



44. Callipepla 



45. Cyrtonyx 



46. Meleagris 

 17. 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- 



