104 Recently published Ornithological Works. 
3. Ridgway on the genus Leucosticte. 
[Sexual^ Individual, and Geographical Variation in the Genus Leuco¬ 
sticte. By K. Kidgway. Field and Forest, ii. Sept. 1876.] 
Quantity of specimens we should have thought would at 
least have tended to produce unanimity of opinion as regards 
the specific value of obscure species of birds. But that this 
is not always the case is shown by the diverse views held by 
Mr. Bidgway and Mr. J. A. Allen upon the subject of the 
specific distinctions of the members of the genus Leucosticte, 
specimens of which by the hundred have been examined by 
both disputants. Though the species of Leucosticte are not 
unrepresented in our collections, thanks to the generosity of 
our American friends, we have not sufficient materials in this 
country to form an independent opinion on so delicate a point 
as to whether certain forms possess well-defined sexual 
differences or not. Mr. Bidgway seems to have gone very 
thoroughly into the subject; and so also has Mr. Allen; and 
we have no doubt the truth will be threshed out between 
them. 
4. Ridgway on the Birds of Guadalupe Island. 
[The Birds of G uadaliipe Island discussed with reference to the present 
Genesis of Species. By B. Bidgway. Extracted from the Bull, of the 
Nuttall Orn. Club, ii. July 1877.] 
This is an interesting paper inspired by a further con¬ 
sideration of the birds inhabiting the little island of Guadalupe, 
Avhich lies off the coast of California. A visit to it by 
Dr. E. Palmer a short time ago brought to light a curious 
series of facts relating to its fauna and flora, the birds being 
found, though generically the same, to be all specifically 
different from their continental allies. Mr. Bidgway now 
examines the avifauna, after the plan adopted by Salvin in 
his recent memoir on the birds of the Galapagos Islands 
(Trans. Z. S. ix. p. 447 et seqq.), and comes to the conclusion 
that the immigration and differentiation of species in 
Guadalupe Island have been substantially the same as in the 
Galapagos archipelago, but that the process of change, either 
through shortness of time or slowness of operation, has not 
