THALASSIDllOMA. STORM-PETREL, 447 



medial prominent line. The tongue somewhat triangular, 

 much flattened, toward the end horny and pointed. The 

 oesophagus of moderate width, but enlarged below into an 

 enormous proventricular sac, covered with scattered glandules, 

 and at its lower part recurved toward the right side, so that 

 the stomach, which is small, elliptical, and muscular, is 

 reversed in position. In consequence of this derangement, 

 the pylorus is placed on the left side, and the intestine arched 

 upward and to the right, before forming the usual duodenal 

 curve. The intestine is rather long and narrow, with small 

 coeca or none, and a globular cloaca. 



Nostrils small, tubular, placed close together, and opening 

 on the ridge. Eyes rather small, with the eyelids feathered. 

 Aperture of ear rather small. Legs slender, placed well for- 

 ward; the tibia long, bare for about a fourth; the tarsus 

 moderate or rather long, very slender, little compressed, an- 

 teriorly reticulate. The hind toe extremely diminutive, with 

 a small conical claw ; the fore toes rather long, slender, 

 scutellate, the third longest, the fourth little shorter ; the 

 interdigital membranes striated, and emarginate. The ante- 

 rior claws are small, little arched, compressed, rather acute. 



The plumage is full, very soft, and blended. The wings 

 very long and narrow, with twenty-four quills ; the primaries 

 very long, tapering, and obtuse, the second longest, the third 

 longer than the first. The tail moderate or long, of twelve 

 broad soft feathers ; but varying in its termination, being 

 cuneate, rounded, even, and emarginate or forked in different 

 species. 



The predominating colours are greyish-black and sooty 

 brown. The sexes are similarly coloured, and the young 

 differ only in having the tints lighter. The Petrels are in a 

 great measure nocturnal, being most active in the dusk, 

 during the summer nights, and in gloomy weather. During 

 winter and spring they roam over the seas, and in the begin- 

 ning of summer collect in bands, which resort to particular 

 breeding-places, on headlands, or unfrequented islands. They 

 nestle in the crevices of rocks, in holes in the turf, or under 

 stones on the beaches. The female lays a single, large, 

 elliptical, white egg. The young remain in the nest until 



