14 EINAR LONNBERG 



Pterodroma (Aestrelata) cooki defilippiana Gigl. & Salvin. 

 Santa Clara: i J* Vs. ^ ? "/s. i J", i ? Vs 191 7- 



The total length of two females has been recorded hy Mr. BackSTROM 

 to measure 320 and 315 mm. respectively. The length of wing in the two 

 males is 227 and 232,5, in the two females 216 and 229 mm. The length of 

 the culmen varies from 26 to 29,3 mm. in these specimens. They thus agree 

 completely with the original description (Ibis 1869s p. 64). 



Concerning this species Mr. Backstrom has communicated the following 

 notes: »During my first stay on the islands, Dec. — April, this bird was not to 

 be seen, but on my return in August it was rather plentiful. It bred under 

 big boulders down at the shore of Santa Clara, but was not found on Masa- 

 tierra. It had not build any nest. According to the inhabitants it laid eggs 

 in September. » 



The difference in breeding habits between this Petrel and the following 

 closely allied species of Masafuera is especially noteworthy. 



Two eggs of Pt. defilippiana colected by Mr. Backstrom on Santa Clara 

 the 9th of August 1917 hava the following measurements: a) 48 mm. long and 

 36,7 mm, broad, b) 49 and 35 respectively. 



The breeding habits of this Petrel are evidently very different from those 

 of the burrowing Pt. cooki cooki, and this together with the difference in 

 external appearance speaks strongly against LooMis' opinion that they should 

 be identical. 



Pterodroma (Aestrelata) cooki masafuerae n. sp. 

 Masafuera: i $ ^"'/a (Dr. Skottsberg), 3 c^J^cT, 2 ?? ^^2 1917. 

 The measurements of these specimens are as follows: 



By having the head and hind-neck blackish, much darker than the grey 

 back, this Petrel is easily recognized as different from its relative defilippiana 

 from the sister island. The measurements also prove that the latter is con- 

 siderably larger and has a much stouter bill. 



The least height of the bill just in front of the nasal tubes is in defi- 

 lippiana as a rule, about 8 mm. in a dry state (in one specimen only 7,4 mm.) 

 but in the Petrel from Masafuera it does not generally exceed 7 mm. and is 

 often less. The hook of the bill of the latter is also more slender etc. 



The general colour of the back of defilippiana is paler and more bluish 

 than in the smaller species. The former has also more white on the forehead 



