S44 Mr. D. A. Bannermau un the [Ibis, 



and water on tlie surface of the earth. Tlie Atlantic 

 Islands^ at any rate the Canaries, were probably formed in 

 the Miocene. The Hawaiian Ishuids are apparently of 

 earlier date, and it was during, or prior to^ the Eocer>e that 

 the Atlantic and Pacific Oceans were joined — for tlie isthmus 

 of Panama had not tlien appeared above the waves. Thei'e 

 was then free communication between the two oceans, 

 the fauna of which was similar in certain features. As a 

 relic of this fauna we raay instance the curious Blenny 

 {Enneanectes curininalis) which was found by Dr. Lr)we on 

 the Atlantic side of the isthmus and which had previously 

 only been known from the Pacific. Once the continents 

 of North and South America were connected by land, an 

 insuperable barrier would prevent the birds on the Pacific 

 side from having any communication with the birds on the 

 other. Bulwer's Petrel (and prol)ably other forms as well) 

 would then be isolated on the Hawaiian Islands and cut oft' 

 from intercourse with the species on the Atlantic side. 

 Each would tend to difi^erentiate, but being sea-roving species, 

 when conditions are much alike, they would naturally not 

 be infiuenced by such diverse factors as if they had been 

 land bii'ds. As a result, the re|)resentatives of Bulwer^s 

 Petrel in the Atlantic and in the Sandwich and Bonin 

 islands in the Pacific are very slightly difterentiated, and 

 have until quite recently been considered identical. 



Whether Bulwer^s Petrel ever inhabited any of the islands 

 oft' the Atlantic coast of Ainerica is unknown. If it did so 

 it has long been exterminated and no trace of its former 

 existence in this region has been left. The evidence seems 

 to point to the conclusion that the Canarian Bulwer's Petrel 

 is descended from the Pacific birds, and not the Pacific 

 subspecies from the typical Atlantic form. An even more 

 remarkable fact in the distribution of Bulwer's Petrel was 

 pointed out by Messrs. Jredale and Mathews (Ibis, 1915, 

 pp. 607, 608) . These authors note the difficulty of separating 

 even subspecilically Atlantic Island birds from those of the 

 Sandwich Islands and the Bonin Islands, while in the Piji 

 Islands a distinct species oi Bulweria occurs. 



