ORNITHOLOGICAL EXPLORATIONS. 341 



80 per cent, of the marine natatores are peculiar to the Pacific. Even 

 more striking, perhaps, is the proportion of the genera, since of twenty 

 genera not less than six, or 30 per cent., are peculiar. 



i^ot less remarkable is the fact that nearly all the Pacific forms are 

 to be found among the marine natatores, since of the one hundred and 

 forty-two species which belong to other categories only one, viz, Arqua- 

 tella couesi, a wader, can be designated as strictly and exclusively Pacific. 



If we now look at the remaining swimmers, fluviatile and fluvio-ma- 

 rine, we will find that the great majority of them, or 70 per cent., are 

 Oircumpolar or Palsearctic, only the following eleven species being 

 exceptions : 



Table XI.— Fluviatile Natatores not Gircumpolar nor Palcearctio. 



Colymbus holbcellii. Cygnopsis cygnoides. 



Sterna camtschatica. Eunetta falcata. 

 Auser segetum middendorffi. formoea. 



albifrons gambeli. Oidemia araericana. 

 Branta canadensis hutchinsii. deglandi. 



nigricans. 



Of these more than one-half (six) are species which are also generally 

 distributed in America. While, therefore, these forms indicate a certain 

 influence of that continent, the character and real insignificance of this 

 influence is manifested by the fact that in the other divisions only two 

 species are American, viz, one wader and one percher, Pelidna alpina 

 pacifica and Acanthis hornemannii exilipes. The number of American 

 forms is surprisingly small indeed. 



While thus the American element is smaller than might, perhaps, be 

 expected, the Circumpolar and Palsearctic forms are quite predominant, 

 as a matter of course, making not less than 43.4 per cent, of the whole 

 number of species, or nearly 52.5 per cent, of all the species, minus those 

 of the water birds which are peculiarly Pacific. (Table TV.) 



Table XII is prepared to show at a glance the number and percent- 

 age of the species of each division as contained in the different ornitho- 

 geographical categories. 



