274 PROCEEDINGS OF THE ACADEMY OF [1883. 



the dispersal of severa,! other classes of land animals, such as the 

 mammals, reptiles, moUusks, etc. And yet it is largely, indeed it 

 might be said almost wholly, upon the distribution of birds that 

 the principles of zoogeography, with its existing classification, 

 were originally sketched out. Granting, however, for the sake of 

 argument, the justice of plea made, are the results in an}^ way 

 materially affected or altered ? Most emphatically not, as will 

 be made manifest b}^ an examination of the accompanying tables, 

 where the original and new (or reduced) data are placed immedi- 

 atel}^ under each other : — 



Of 26 Nearctic families (land and marine) 19 are also Paliearctic 



^14 per cent. 

 Of 23 Nearctic families (land only) 16 are also Paljearctic = 



10 per cent. 

 Of 74 Nearctic genera (land and marine) 35 are also Pahiearctic 



= 4*1 per cent. 

 Of 62 Nearctic genera (land only) 26 are also Palaearctic = 



42 per cent. 

 Of 74 Nearctic genera (land and marine) 26 are peculiar = 



35 per cent. 

 Of 62 Nearctic genera (land only) 23 are peculiar = 37 percent. 



The 26 peculiar Nearctic genera (land and marine) comprise 

 60 species, or 21 per cent, of the entire number (279) of species. 



The 23 peculiar Nearctic genera (land only) comprise 57 species, 

 or 21 per cent, of the entire number (267) of land species. 



It will thus be seen that the greatest variation in any place is 

 only five per cent. If, as has been done in my paper, we unite 

 the Nearctic and Palaearctic regions, we will then have, as 

 claimed : — 



86 peculiar genera (land and marine) out of a total of 139 = 62 



per cent.; or, deducting the marine forms — 

 74 peculiar genera out of a total of 127 land forms = 58 per 



cent. 

 And if we consider the specific forms represented by these 

 peculiar genera, we have — 



284 out of a total of 675 (land and marine) = 42 per cent. ; or, 



deducting the marine forms — 

 264 out of a total of 655 land forms = 40 per cent. 



