Petrels from the North-East Pacific Ocean. 589 



commonly observed. It was almost impossible to write down 

 the differences, and practically no one has attempted to 

 do so. Neither Cones nor Ridgway were as happy in their 

 diagnoses in connection with these as with most groups, 

 yet their association of the species was correct. 



Neither Salvin nor Godman attempted any generic dia- 

 gnosis, the keys given being inaccurate when the species were 

 examined. Yet by means of colour and form these groups 

 can be separated, and that they are very distinct groups is 

 proved by study of the nestlings, as was first shown by 

 Mathews. 



Pterodroma always has a black bill ; Puffinus never has, 

 though sometimes almost a unicolorous bill. The main 

 difference, and one which is quite diagnostic, is in the 

 colour of the legs and feet. 



In Pterodroma the feet may be black : we note this first, 

 as it is a very rare occurrence and principally when the bird 

 is very dark and unicolor. Even then, the majority of birds 

 show bicoloured feet. The distribution of colour in the feet 

 forms a generic or super generic feature. The tarsus and the 

 proximal joint of the toes is wholly light -coloured, the remainder 

 being dark. This is easily seen in skins, and most figures 

 show it. 



Puffinus never has the legs and feet black, but always more 

 or less bicoloured. The distribution of colour in the feet forms 

 a generic or subgeneric feature. The outside of the tarsus and 

 the outer toe are always dark when compared with the inside 

 and innei' toes. In the majority of cases this is very promi- 

 nently seen, the outside being blue-black and the inside 

 yellow. In both cases nestlings in down show these diverse 

 styles of leg and feet coloration. 



The genus Puffinus covers, in the 'Monograph of Petrels,' 

 twenty-five species, as follows : — P. leucomelas (Temm.), 

 cuneatus Salvin, bulleri Salvin, chlororhynchus Less. 

 [=pacificus (Gmelin)), gravis (O^Reilly), kuhli (Boie), 

 edivardsi Oustalet, creatopus Cones, anglorum (Kuhl) ( = 

 puffinus Briinnich), yelkouanus Acerbi, opisthomelas Coues 

 (= couesi Mathews), auriciilaris Townsend { = opisthomelas 



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