May 14, 1897.] 



SCIENCE. 



771 



tion among these birds in life, and owing fur- 

 ther to the fact that certain species are on the 

 verge of extermination, while others doubtless 

 still remain to be discovered, it is clearly of 

 pressing importance that some competent 

 ornithologist should visit the islands and study 

 the habits and interrelations of the various 

 forms before it is too late. 



In recent years relatively large collections of 

 birds have been made on some of the islands. 

 Those obtained by the naturalists of the ' Alba- 

 tross ' in 1888 and 1891, and by Dr. George 

 Baur and Mr. Adams in 1891, were brought to 

 the U. S. National Museum, where they have 

 been critically studied by Mr. Ridgway. The 

 result is the present admirable paper entitled 

 'Birds of the Galapagos Archipelago,' one of the 

 most important ornithological publications that 

 has appeared in many years. It is a compre- 

 hensive treatise ' intended,' as the author tells 

 us, ' to embody practically all that it known of 

 the avi-fauna ' of the region. Still "it does not 

 claim to be exhaustive, for a great deal has yet 

 to be learned before anything like a complete 

 exposition of the subject is possible." 



Respecting the conflicting theories as to the 

 origin of the Galapagos Mr. Ridgway states : 

 ' ' All writers are agreed that the Galapagos 

 Islands are volcanic ; nearly all, from Darwin 

 to Agassiz, agree that they were uplifted from 

 the sea by volcanic action, and that their up- 

 heaval therefore antedates the advent of or- 

 ganic life upon them. Dr. Baur, however, be- 

 lieves that these islands are the higher points 

 of an extensive submerged area, whose subsi- 

 dence took place after a fauna and flora had 

 been acquired ; or, to quote his own words : 

 ' At a former period these islands were con- 

 nected with each other, forming a single large 

 island, which itself at a still earlier time was 

 united to the continent, probably with Central 

 America and the West Indies. ' ' ' 



Mr. Ridgway modestly adds that he is " not 

 competent to discuss the relative merits of these 

 two opposite theories from the physiographer's 

 standpoint ; but if the apparent relationships 

 of the fauna have any bearing on the question," 

 he believes Dr. Baur's theory ' at least worthy 

 of serious consideration.' He calls attention 

 to the map accompanying Alexander Agassiz's 



report on the cruise of the 'Albatross ' for 1891, 

 which shows that the Galapagos and Cocos Is- 

 lands stand on a submarine plateau covered by 

 only 1,500 fathoms of water, and that this 

 plateau reaches northeasterly to within 100 

 miles of the present coast of Central America, and 

 is only a little more than 30 miles distant from 

 the 1,500-fathom coast-line. These distances are 

 too insignificant to form any barrier to the free 

 passage of birds ; hence, if it can be assumed 

 that the present submarine plateau was ever 

 above the level of the sea it would naturally 

 have received its original bird population from 

 Central America. Let us see how this accords 

 with the facts of present distribution. Mr. 

 Ridgway tells us that 38 genera of birds are 

 believed to breed on the islands. Of these, 

 23 are wide ranging, 6 * are peculiar to the 

 islands, and 7 are tropical American. Elimi- 

 nating the wide-ranging genera, 13 remain, of 

 which 6 are peculiar and all of the others trop- 

 ical American. Mr. Ridgway then takes up the 

 5 * peculiar genera and discusses each with re- 

 spect to its relationships and probable origin. 

 After stating that two of these are clearly of 

 American origin, that two resemble both Ameri- 

 can and Hawaiian types, and that the remain- 

 ing one "has no very near relative among the 

 known continental or West India birds, but in 

 general appearance is very much like a smaller 

 'edition' of the Hawaiian genus Oreomyza," he 

 sums up as follows : "Of the five peculiar 

 'Galapagoan genera of birds, only two (Neso- 

 mimus and Nesopelia) are of evident American 

 relationship. The remaining three have so 

 obvious a leaning toward certain Hawaiian di- 

 cseidine 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 

 that the resemblance of Cocornis, Cactornis and 

 Camarhynchus to the above mentioned Hawaiian 

 forms is merely a superficial one, and not indica- 

 tive of real relationship. I do not by any 



* By a singular slip the number of peculiar genera 

 given in the tables and on page 465 is 6, while two 

 pages later it is reduced to 5. The latter number is 

 the result of uniting Cadornis with Geospiza after the 

 earlier pages were written. By an oversight this was 

 not corrected in the proof. 



