FORKED-TAILED PETREL. 437 



Thalassidroma Leachii, Ch. Bonaparte, Synops. of Birds of the United States, 



p. 367. 

 Phocellaria Leachii, Temm. Man. d'Ornith. part ii. p. 812. 



Adult Male. Plate CCLX. Fig. 1. 



Bill shorter than the head, slender, straight, with the tips curved, as 

 broad as high at the base, extremely compressed at the end Upper 

 mandible with the nostrils forming a tube on its ridge at the base, beyond 

 which the dorsal line is for a short space straight, then decurved, the 

 ridge narrow and separated from the convex sides by a narrow groove, 

 the edges sharp, inflected, the tip compressed, incurved. Lower man- 

 dible with the angle rather long, narrow and pointed, the dorsal line be- 

 yond it decurved, the sides erect, the edges sharp, the tip decurved. 



Head of ordinary size, roundish, anteriorly narrowed. Neck short. 

 Body rather slender. Feet rather long, slender ; tibia bare at its lower 

 part ; tarsus slender, reticulate all round. Hind toe minute, with a coni- 

 cal claw ; anterior toes of moderate length, slender, scutellate above, con- 

 nected by striated webs with concave margins ; the third and fourth toes 

 longest, and about equal. Claws slender, arched, compressed, acute. 



Plumage very soft, blended, the feathers distinct only on the wings, 

 which are very long ; primary quills tapering but rounded, the outer four 

 a little incurved at their extremities, the second longest, the third almost 

 equal, the first and fourth about the same length, the rest rapidly gra- 

 duated ; outer secondaries incurved, obliquely rounded ; inner longer, 

 tapering, straight. Tail deeply forked, of twelve broad, rounded feathers. 



Bill and feet black. Iris dark brown. The general colour of the 

 plumage is dark greyish- brown, the quills and tail brownish-black, the 

 smaller wing-coverts and inner secondaries light greyish-brown ; the rump, 

 sides of the abdomen, and exterior lower tail- coverts, white. 



Length to end of tail 8 inches, to end of wings 8i ; extent of wings 

 I85 ; wing from flexure 6J ; tail 3 ; bill along the back ^%, along the 

 edge of lower mandible \^ ; tarsus 1 ; middle toe !§, its claw j^. Weight 



The Female is exactly similar to the male. 

 Adult Female. Plate CCLX. Fig. 2. 



