Auk 
330 feecent Literature. July 
volcanic, and Dr. G. Baur’s theory that they are the remnants of a 
former large oceanic land area—and presents the evidence afforded by the 
birds. He considers in this connection the relationships of the five 
peculiar Galapagoan bird genera, and finds that only two ‘‘ are of evident 
American relationship. The remaining three have so obvious a leaning 
toward certain Hawaiian Diczidine forms that the possibility of a former 
land connection, either continuous or by means of intermediate islands 
as ‘stepping stones, becomes a factor in the problem. It may be,” he 
adds, that the resemblance of these three genera to “‘ Hawaiian forms is 
merely a superficial one, and not indicative of real relationship. I do 
not by any means claim, on the strength of such evidence, a common 
origin for them, but merely present the facts as ‘food for reflection.’ ” 
In this connection Mr. Ridgway gives a summary of the ranges of the 
genera of Galapagoan birds, without, however, deriving from this study 
any decisive evidence as to ‘‘ whether the non-peculiar portion of the 
Galapagoan avifauna is most nearly related to that of the adjacent main- 
land of South America or that of lower Central America or the West 
Indies.” 
Mr. Ridgway comments on the perplexing difficulties that beset the 
discrimination of the many closely related forms, and says that “when. 
ever there seemed to be a well-defined average difference between speci- 
mens from different islands, I have not hesitated to separate them as local 
forms. No other course, indeed, was practicable; for were ‘lumping’ 
once begun there could be no end to it, unless purely arbitrary limits 
were given to the species recognized, and if followed to a logical conclu- 
sion might easily end in the recognition of a single variable species, 
equivalent in its limits to the genus.” 
The distribution of the 105 species thus far recorded from the Galapagos 
Archipelago is shown in a series of tables, as to the group of islands 
collectively, and for each island individually. Then follows the detailed 
treatment of the species, with charts showing their distribution in the 
Galapagos Islands. It is interesting to observe that five-sixths (53 
species) of the Passerine birds belong to four genera — WVesomimus, Cer- 
thidea, Geospiza, and Camarhynchus— peculiar to the Galapagos, and 
that half the remainder belong to the genus Pyrocephalus ; and that all 
but two of the 61 species of Passerine birds are peculiar to the Islands, 
the other two being of casual occurrence. Most of the remainder are 
wide-ranging water birds, with a few species peculiar to the Galapagoan 
fauna. 
The species are treated exclusively from the systematic standpoint, 
giving their synonymy and bibliography, with full descriptions, tables of 
measurements, and their ranges, together with discussions of their relation- 
ships. The paper concludes with a bibliography of all the works and 
papers relating to Galapagoan ornithology. Mr. Ridgway has thus given 
us a detailed and masterly monograph of the birds of the most interesting 
and instructive group of islands known to science.—J. A. A. 
