MONOGRAPH OF THE PETRELS. 



delicate blue tint of the upper surface. There is, however, considerable variation in 

 this respect, as also in the blackish stripe which extends behind the eye down the sides 

 of the neck, and is sometimes distinct, but at other times scarcely perceptible. 



No actual limits as to width of bill can be drawn between P. vittatus and 

 P. banksi, neither can the exact differences in the proportions of the bills of P. banksi, 

 P. brevirostris, and P. desolatus be defined. There seems indeed to be a perfect 

 gradation between all these Blue Petrels, and it is impossible to say where one form 

 ends and the other commences. 



The following are the measurements of a series of P. desolatus in the British 

 Museum : — 



Length of Culmen. Breadth of Culmen. Wing. Tarsus. Middle toe and claw. 



0.9-1.05 0.45-0.5 7.1-7.4 1.2-1.35 1.3-1.6 



This species was discovered during Captain Cook's first voyage, and a specimen 

 captured in Lat. 59°, was figured by Sydney Parkinson. On this drawing, which is 

 only a pencilled outline, in the Banksian Collection of pictures in the British Museum, 

 the name of Procellaria turtur was founded by Kuhl. The oldest name, however, is 

 that of P. desolata of Gmelin, founded on the " Brown-banded Petrel " of Latham, 

 described from an example in Sir Joseph Banks' Collection, and procured on Desolation, 

 or Kerguelen, Island : it is doubtless the specimen obtained by Captain Cook. 



Examples of this and the allied species have a band of black across the upper- 

 surface of the body which, according to Gould, looks like a black W when the wing 

 is expanded. It seems strange that Latham named the bird the " Brown-banded 

 Petrel," but it should be noticed that Dr. E. A. Wilson states that P. banksi, as seen 

 from the " Discovery," in some lights completely lost its blue colour, and appeared 

 to be pale brown, conveying the idea that two different Petrels of the same size 

 composed the flock (Nat. Antarctic Exped., II., Aves, p. 106). 



Gould believed that this Blue Petrel traversed the whole surface of the Atlantic 

 and Pacific Oceans, between the 30th and 50th degress of south latitude, as he saw 

 and frequently killed specimens while sailing within the above limits ; he also shot it 

 in company with P. banksi, and it appears to have a similar range, being equally 

 numerous in the temperate latitudes of the Pacific and the Atlantic Oceans. 



During the voyage of the " Magenta " Professor Giglioli found this Prion 

 sometimes in small, and at other times in large numbers. The first was seen on March 

 16th, 1866, in Lat. 42° 54' S., Long. 44° 46' E. ; up to the 18th of that month there 

 were fewer seen. Four days later many hundreds were observed in Lat. 41° S., Long. 

 66° 04' E. On the journey between Batavia and Melbourne this Blue Petrel was noticed 

 from April 23rd in small parties (Lat. 37° 22' S., Long. 112° 5' E.) till the 28th of the 

 same month Lat. 39° 36' S., Long. 126° 25' E; in the Pacific the species'was scarcer, 

 a single example being captured in Lat. 36° 36' S., Long. 89° 54' W. On November 



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