72 NORTH AMERICAN BIRDS. 



a}. Lower tail-coverts and belly white. 



h^. Throat and collar round hind-neck white ; length 8.75-9.00 ; tail emarginated 

 for about .75 ; tarsus 1.65-1.75, middle toe, with claw, 1.25, or more. 

 Hab. Intertropical seas. 



C. tropica (Gould). Tropical Petrel.' 



V^. Throat usually with only concealed white, and without white on hind-neck ; 



length 7.50-8.00, wing 6.00-6.50, tail 3.00-3.30, even; tarsus 1.40-1.60, 



middle toe, with claw, 1.05-1.10. Hah. Intertroj^ical seas, north, 



casually, to coast of Florida. 



110. C. grallaria (Vieill.). White-bellied Petrel. 

 a?. Lower tail-coverts and belly dusky. 



No white on hind-neck, but throat sometimes white, and feathers of 

 forehead white beneath surface ; dusky of belly usually connected with 

 that on chest ; length 8.50-8.75 ; tail usually emarginated for about .75 ; 

 wing 6.25-6.75, tarsus 1.60-1.70, middle toe, with claw, 1.05-1.15. Hab. 

 South Pacific. 



C. melanogaster (Gould). Black-bellied Storm Petrel.^ 



Genus PELAGODROMA Eeichenbach. (Page 56, pi. XV., fig. 2.) 



Species. 



Forehead, superciliary stripe, and lower parts, pure white; top of head, broad 

 stripe behind eye, and upper parts generally, slate-color, sometimes inclining to 

 plumbeous ; upper tail-coverts light ash-gray ; quills and tail-feathers blackish ; 

 bill black ; tarsi deep black ; feet black, the webs mostly yellowish ; wing 5.90-6.40, 

 tail 2.90-3.30 (forked for .25-.35), tarsus 1.52-1.70, middle toe, with claw, 1.37-1.40. 

 Hab. Southern seas, accidental off coast of Massachusetts. 



111. P, marina (Lath.). White-faced Petrel. 



1 Thalassidroma tropica Godld, P. Z. S. 1837, 366. 



2 Thalassidroma melanogastra Gould, Ann. Mag. N. H. xiii. 1841, 367 ; B. Austr. vii. 1818, pi. 62. 



