observed at the Salvage Islands. 53 



Piton, -where there are neither rats nor mice to interfere with 

 them. 



The following measurements are taken from a number of 

 adults of both sexes, and we find that the males on the 

 average are distinctly smaller than the females, though this is 

 not apparent from the condensed measurements given below. 

 The average male wing is 6"25, that of the female 6'38. 



A large series of eggs measures 1*35-1'48 by l*0-l-08 inch. 



-f-20. OCEANODROMA CRYPTOLEUCURA. 



Cymochorea cryptoleucura, Ridgw. Proc. U. S. Nat. Mus. 

 iv. p. 337 (188.2). 



Almost more interesting than the white-breasted species 

 was the square-tailed, white-rumped Petrel, of which we 

 obtained but a single example, caught at night by our men 

 on Great Salvage, though we saw several flying over the 

 neighbouring seas from the deck of our steam-tug. This 

 bird had not yet come. to shore to breed, and the only egg 

 ■we obtained was taken on the Lime Island, Porto Santo, in 

 the month of June. It had always been previously supposed 

 that the only small white-rumped Petrel with black webs to 

 the feet met with in these seas was Leach's fork-tailed 

 Petrel (0. leucorrhoa). That this bird also occurs there is 

 certain, for we have seen a specimen obtained at the 

 Canaries by Mr. Meade- Waldo, but it would appear to be 

 merely a straggler so far south, and certainly the square- 

 tailed species is the bird that has generally been mistaken 

 for it. O. cryptoleucura was described a few years ago from 

 the Sandwich Islands, and no one had any idea that it was 

 also found in the Canary Seas, so that this discovery is a 

 matter of considerable interest to ornithologists. The 

 birds obtained at St. Helena also belong to this form, and 

 not to Leach's Petrel, as has been generally believed. It 

 may be useful to state the main differences between the two. 



