362 THE TUBE-NOSED SWIMMERS — TUBINARES. 



Family PEOCELLARIID^. — The Petrels. 



The North American genera, of this family are numerous, and may be distinguished 

 as follows : — 



PROCELLARIIN^. Secondaries 13 or more ; tarsi covered with small hexagonal scutellai ; 

 claws sharp, curved, more or less compressed. Leg-bones shorter than wing-bones ; 

 cervico-dorsal vertebra) not less than 22 ; basal phalanx of middle toe shorter than the 

 next two joints, together. 



A. Size very large (wing, 17.00 inches or more). Bill longer than tarsus. 



3. Ossifraga. Tail of sixteen feathers ; bill longer than the tarsus, very stout ; nasal tube 



nnicli longer than the maxillary unguis, the nasal orifice single at the entrance, the septum 

 being hidden. 



B. Size medium (wing less than 14.00 inches, and more than 7.00). Bill shorter than tarsus. 



4. Fulmarus. Tail of twelve to fourteen feathers ; bill very stout ; nasal tube much shorter 



than the unguis, straight on top ; maxillary unguis separated from the nasal tube by a 

 very narrow space. 



5. Priocella. Similar to Fulmarus, but bill much more slender, the nasal tube concave on 



top, and separated from the unguis by a very wide space. 



6. Priofinus. Tail-feathers twelve ; nasal tubes about half as long as the unguis, and sepa- 



rated from the latter by a space equal in length to about two thirds the length of the 

 unguis ; nostrils opening directly anteriorly. 



7. PufEnus. Tail-feathers twelve ; nasal tubes about half as long as the unguis, and sepa- 



rated from the latter by a space nearly ec[ual to the length of the unguis ; nostrils opening 

 obliquely upward. 



8. CEstrelata. Bill much compressed and very deep, the ungui very large, occupying nearly 



the terminal half of the bill ; nasal tubes short and very prominent, about one third to 

 one half as long as the maxillary unguis, the nostrils opening directly in front. 

 9 Bulweria. Similar to CEstrelata, but smaller and more slender, the tail longer (about 



half the wing) and more graduated. Myological formula said to be very different. 

 10. Daption. Tail of fourteen feathers ; bill broad and depressed, except terminally, the 

 unguis occupying less than one third its length ; nasal tubes depressed and concave in 

 the middle, nearly as long as the unguis, and separated from the latter by a space equal 

 to about two thirds its length ; maxillary rami separated below from the angle back, 

 bowed slightly outward, the intervening space occupied with bare skin ; tarsus much 

 longer than the bill, but shorter than the middle toe. 



C. Size very small (wing less than 7.00 inches). 



11. Halocyptena. Tail much rounded, or slightly graduated ; tarsus decidedly longer than 

 the middle claw (about twice the culmen) ; no white on the rump. 



12. Procellaria. Tail even or slightly rounded ; tarsus about equal to the middle toe and 

 claw (about twice the culmen) ; a white patch on the rump. 



13. Cymochorea. Tail much forked ; tarsus about as long as, or a little shorter than, the 

 middle toe and claw (about one and a half times as Imig as the culmen) ; with or without 

 a white rump patch. 



14. Oceanodroma. Tail forked, the feathers scalloped at the end, the lateral rectrices 

 narrowed terminally ; tarsus about equal to, or very little shorter than, the middle toe 

 and claw (not quite twice as long as the culmen) ; no white on the rump. 



OCEANITINiE. Secondaries 10 ; tarsi ocreate, or else covered in front with large obliquely 

 transverse scutes ; claws flat and broad. Leg-bones longer than wing-bones ; cervico- 

 dorsal vertebrae 21 ; basal phalanx of middle toe lunger than the next two together. 

 Nasal aperture single, circular. 



