532 NATATORES. THALASSIDROMA. 



the base, darker towards the tip, slender, one inch and 

 three-eighths in length from the forehead to the tip. 

 Legs having the tarsi much compressed ; front of the 

 tarsi, and part of the webs and toes yellowish, tinged 

 with flesh-red. 



GENUS THALASSIDROMA, VIGORS. STORM- 

 PETREL. 



GENERIC CHARACTERS. 



BILL shorter than the head, much compressed in front of 

 the nasal sheath, with the tip of the upper mandible sud- 

 denly curving and hooking downwards, and that of the lower 

 one slightly angulated and following the curve of the upper. 

 Nostrils contained in one tube or sheath, but shewing two 

 distinct orifices in front. 



Wings long, acuminate, with the first quill-feather shorter 

 than the third, and the second the longest in the wing. Tail 

 square, or slightly forked. 



Legs having the tarsi rather long and slender, reticulated. 

 Feet of three toes, united by a membrane. The outer and 

 middle toes nearly equal in length, and longer than the 

 inner ; hind toe represented by a small strait dependant nail. 



The members of this genus, which are all of small size, 

 have been very properly separated by Mr VIGORS from the 

 rest of the Petrel group, as they exhibit a decided difference 

 jn the form of the bill from that of the Shearwaters and the 

 other nearly allied species, the lateral compression towards 

 the tip being much greater ; and the nostrils, instead of being 

 separate tubes, contained in a common sheath, and merely 

 divided by an internal septum. The proportions of the wing 

 are also different, and their legs are longer and placed more 

 in the centre of the body. In TEMMINCK'S " Manuel," they 



