Vor. II, Pt. 11] LOOMIS—A REVIEW OF THE TUBINARES 39 
V 
CLASSIFICATION AND NOMENCLATURE 
° GENERAL OBSERVATIONS 
Species.—Bird species are realities, not concepts, and their 
identification is not in any way dependent upon a knowledge 
of their distribution. A bird species presents a peculiar as- 
semblage of characters that separates it from all other bird 
species as absolutely as one island is separated from all other 
islands. A bird species may vary but little, as the Laysan 
Albatross, or it may have a wide range of variation, as the 
Wedge-tailed Shearwater; for it is not degree of variation, 
but absence of intergradation that gives specific. value to 
characters. 
Groups of Species—In nature, groups of bird species 
abound, but there is not sufficient coordination among them 
to permit any arrangement that is not largely arbitrary. 
Under such conditions, it is not surprising that systems have 
multiplied, and that there exists to-day much diversity of 
Opinion respecting taxonomic values. These points are well 
illustrated in the following schemes of classification of the 
albatrosses, petrels, and diving petrels: 
Mr. Evans (Cambridge Natural History, Vol. IX; essentially 
Dr. Gadow’s Scheme in Bronn’s Thier-Reichs) 
Diomedeinz 
Oceanitinz 
Procellariinze 
Pelecanoidinz 
Order Procellariiformes Suborder Tubinares Procellariide 
Mr. Satvin (Monographs of Mr. Salvin and Dr. Godman) 
Procellariide Procellariinz 
Oceanitinz 
ee Puffinine 
Puffinide I 
Order Tubinares Fulmarinz 
Pelecanoidide 
Diomedeidz 
