Black: tail forked; the wings not reaching beyond its tip: tarsus eleven lines and a half.
P. Leachii, Temm. Man. d'Orn. torn. ii. p. 812. Leach's Petrel, Steph. in Shows Gen. Zool. vol. xiii. part i. p. 219. pl. 25. Fork-tailed Petrel, Bew. Brit. Birds, vol. ii. p. 244. Selb. Illust. vol. ii. p. 537. pl. 103v f. 1.
Entire length seven inches six lines.
Head, neck, and under parts, grayish black: back and scapulars pitch-black: quills black; the coverts lighter, forming a bar of dusky brown: upper and lateral under tail-coverts white, the shafts and tips black: tail black, of twelve feathers, forked; the depth of the fork half an inch: bill and legs black. (Egg). White; roundish-oval: long, diam. one inch four lines; trans, diam. eleven lines.
First discovered by Mr. Bullock in St. Kilda. Since ascertained to be not uncommon in that island, though rare elsewhere. Solitary individuals have been occasionally met with in different parts of England. Breeds in the clefts of rocks, and lays one egg. Food and habits similar to those of the last species.
I am informed by Mr. Yarrell that this species has been killed in the British Channel, though at some distance from land. It inhabits the western shores of the Atlantic, and is principally distinguished by a large oblong yellow spot on the membranes of the toes. Length of the tarsus nearly an inch and a half.