NO. 1116. PBOCEEDINGS OF THE NATIONAL MUSEUM. 461 



nally fouud; as the largest of tlie ground linches {Geo.sjiiza magniros- 

 tris), -wiiicli seems no longer to inliabit Charles or Chatham islands, 

 where Darwin collected liis specimens,' and Cam((rhynchu.s variegafns, 

 originally discovered on Abingdon and Bindloe islands, but according 

 to Dr. Baur no longer occuring there.- 



It is evident, therefore, that if we are to acquire a more exact knowl- 

 edge of this classic fauna, an eifort to do so shoukl be made before it is 

 too late. 



I have already remarked that the time has not arrived when we may 

 indulge in speculations as to the origin of the Galapagoan fauna with 

 reason for great confidence in the correctness of any theories which 

 may be advanced. Nevertheless, a few observations on the subject 

 with reference to Dr. Baur's subsidence theory^ as opposed to that of 

 volcanic uplift, together with the possibility of a nou- American element 

 in the composition of the fauna, may not be altogether futile. 



All writers are agreed that the Galapagos Islands are vidcanic; 

 nearly all, from Darwin to Agassiz, agree that they were uplifted from 

 the sea by volcanic action, and that their upheaval therefore antedates 

 the advent of organic life vipon them. Dr. Baur, however, believes 

 that these islands are the higher j^oints of an extensive submerged 

 area, whose subsidence took place after a fauna and flora had been 

 acquired ; or, to quote his own words : " At a former period these islands 

 were connected with each other, forming a single large island, which 

 itself at a still earlier time was united to the continent, ])robably with 

 Central America and the West Indies." '^ 



I am not competent to discuss the relative merits of tliese two oppo- 

 site theories from the physiographer's standpoint; but if the apparent 

 relationships of the fauna have any bearing on the question, I believe 

 Dr. Baur's theory to be at least worthy of serious consideration. 



By reference to the map accompanying Professor Agassiz's report 

 upon the Albatross cruise of 1891,'^ it will be seen that the Galapagos 

 Archipelago and Cocos Island rise from a submarine plateau of 1,500 

 fathoms depression, which at its northeastern extremity approaches 

 within 100 miles of the nearest i)oint of the present coast line of Cen- 

 tral America, being separated from the 1,500-fathom coast line by only 



' Dr. Baur says (Amer. Nat., XXV, 1891, p. 905) thnt be and Mr. Adams collected 

 this species on South Albemarle and .lervis islands; but their specimens were lost, 

 and it is possible that the birds they met with were not the true G. magnirostrifi, but 

 an nndescribed related form. 



It has subsequently been ascertained to inhabit Albemarle, James, Indefatigable, 

 Chatham, and Charles i.slands. The question therefore arises, Has it shifted its range 

 from Abingdon and Bindloe to these islands, or were the original specimens wrongly 

 labeled as to locality f 



^\mer. Nat., XXV. 1891, pp. 217-229, 307-326. 



••The Differentiation of Species on the Galapagos Islands and tlie Origin of the 

 Group. Biological Lectures delivered at the Marine Biological Laboratory of Woods 

 Hole, in the summer session of 1894. Reprint, pp. 67-78. 



6 Bull. Mus. Comp. Zool., XXIII, No. 1, pi. iii. 



