446 



THALASSIDROMA. STORM-PETREL. 



The birds of which this genus is composed are the smallest 

 of those which, being furnished with interdigital membranes, 

 are peculiarly adapted for swimming. Diminutive as they 

 are, and therefore, as one might naturally think, less able 

 than the larger species to withstand the violence of the winds 

 and waves, they are, of all birds, those which venture to the 

 greatest distance from land, being often met with in the very 

 middle of the Atlantic Ocean. As, in searching for food, 

 they fly close to the surface, and while hovering or stooping, 

 let down their'Yeet, and pat the water with them, they seem, 

 as it were, to run on the waves ; whence the name of Thalas- 

 sidroma, or sea-runner, applied to them, as well as that of 

 Petrel, or Little Peter, in allusion to the Apostle. They are 

 of a slender form, having the body very small, compared with 

 the bulk of plumage with which it is covered ; the neck 

 short and slender ; the head ovate, and compressed. 



Bill shorter than the head, slender, much compressed, de- 

 curved at the end, and acute ; upper mandible with the dor- 

 sal line at first direct or concave, then abrupt at the end of 

 the nasal tube, afterwards nearly straight for a short space, 

 and finally much decurved, the ridge elevated and separated 

 by a groove from the sides, which are convex at the base, the 

 edges sharp, sinuate, approximating toward the end, the tip 

 compressed, decurved acute ; the nostrils dorsal, submedial, 

 opening in front by two approximated tubes ; lower mandible 

 A^th the intcrcrural space narrow and ])ointed, the lower 

 outline of the crura decurved, the dorsal line declinate and 

 concave, the edges sharp, approximated or even in contact 

 toward the end, the tip compressed and decurved. 



The mouth of moderate width, but dilatable ; the palate 

 convex, with four ridges, anteriorly Acry narrow, with a 



