PROCELLARIIDiE. 269 



latter belongs to the dark form, but there is a skin in the Pryer col- 

 lection, also collected by Mr. Snow on the Kurile Islands, which is as 

 typical of the light form. 



The Fulmar is a circumpolar species and breeds in great numbers 

 on St. Kilda. It appears to be dimorphic, but, as is common with other 

 dimorphic species, the proportion of dark and light forms varies 

 greatly in different localities. 



264. (ESTRELATA HYPOLEUCA. 

 (BONIN-ISLAND SHEARWATER.) 



(Estrelata hypoleuca, Salvin, Ibis, 1888, p. 359. 



The Bonin-Island Shearwater is blackish brown above, with the 

 feathers of the back and rump margined with grey ; the forehead, 

 lores^ and underparts are white ; the axillaries are white, but most of 

 the under wing-coverts are brown ; quills brown, rectrices white 

 at base. Wing 8|, tail 4| inches. 



The Bonin-Island Shearwater was originally described from an 

 example sent to me by Mr. Snow from Kruzenstern Island in the 

 North Pacific, where it had been obtained in the spring of 1883. 

 The type remained unique in the British Museum until Mr. Hoist 

 sent me adult and young from Nakondo-Shima, one of the Parry 

 Islands (Seebohm, Ibis, 1890, p. 105). 



Family PROCELLARIID^. 



The Petrels appear to be intermediate between the Shearwaters, 

 which they resemble in the position of their nasal tubes, and the 

 Albatrosses, which, like the Petrels, have lost their basipterygoid 

 processes. 



They all possess the ambiens muscle except the genus Fregetta. 



There may be about a score species of true Petrels in the two sub- 

 families, Procellariinse and Oceanitinse, into which the group may be 

 divided. The family is represented in both hemispheres, and three 

 species are recorded from Japan. 



