PROCELLARITD^E. 415 



Family PROCELLARIID^S, OR PETRELS. 



The Petrels are a well-defined group of birds which are probably not very 

 nearly related to any other family, inasmuch as ornithologists cannot 

 agree to which family they have the greatest affinity . Sclater regards them 

 as nearest related to the Gulls, but distantly enough to form an order by 

 themselves. Forbes split them into two families, which he associated with 

 the Herons, Pelicans, and Birds of Prey. Gadow regards the Petrels as 

 nearly allied to the Gulls, but not quite so near to them as the Auks are, 

 the three groups being rather more remotely allied to the Plovers, which 

 he regards as less modified descendants of the ancestors of these four 

 families. 



Although the Petrels are schizognathous in the arrangement of their 

 palatal bones, and were associated by Huxley with the Gulls, the Divers, 

 the Grebes, and the Auks, they were regarded by him as aberrant forms 

 inclining towards the Pelecanidse. Newton regards them as distinct from 

 the Laridse and their allies, so much so as to warrant their being placed 

 in an order by themselves. The number of notches on the posterior 

 margin of the sternum of the Petrels varies in different genera. In 

 Nitzsch's ' Pterylography' it is stated that the tract- formation of the Skuas 

 is elevated into the type of a group in the Petrels. 



Petrels only moult once in the year. The young are born covered with 

 down, but they remain in the nest until they can fly. It is not known 

 whether the young in first plumage moult in their first autumn, when the 

 annual moult of the adults takes place. 



The Petrels are all web-footed birds, with the hind toe either very small 

 or absent. They have long wings, short tails, and hooked bills, but their 

 most important external character is their tubular nostrils. 



They form a large family, containing about a hundred species, which 

 are distributed over the ocean in all parts of the world, approaching the 

 coasts only to breed. 



The Petrels which visit our coasts belong to four different genera, which 

 may be characterized as follows : 



Large birds, with wings 8| inch j PUFFINTTS . . | N a 8al tube s much less than half 

 long or more : first primary ) ' the length of the bill. 



( FULMABUS. 



longest. 



Small birds, with wings 6 inch I PBOCELLARJA. 



long or less : second primary j 0cEANITB8 j Tarsus booted in front, much Ion- 

 longest. ' \ ger than middle toe and claw. 



