
ae ; 
increase the buoyancy of the body in flight, and 
io give direction to the beak upward and downward : 
by lessening or increasing the gravity of the regions 
of the head. A prodigiously dilatable esophagus 
to compensate the want of a pouch for collecting 
and storing food, occurs in the cormorant, phala- 
erocorax carbo, another very marked individual of 
the family of pelicans, and reputed among the most 
voracious of birds. The lower mandible is slender, 
elastic, and dilatable, and comparatively weak, but 
additional pairs of muscles, having been furnished 
them, the structure of the bill combines increased 
‘facility for retaining their prey, with augmented — 
powers for seizing it. The plotuses or darters, 
another very remarkable genus of this curious tribe 
of birds have an excessive length of neck ta fit them 
for pursuits differing from those of the pelicans, 
and the frigate birds; but the peculiar power of 
all is still the versatile gravitation of the body. 
The darter swims with the body surmerged, no 
other part being seen, but the long slender head and 
neck, which appear moving over the stream, like a 
serpent, breasting the waves, half erect. The frigate- 
bird’s capacity is for the air alone; it abandons 
the water altogether, and neither dives nor swims, 
but confines itself to the limitless expanse of the 
ocean from whence alone it derives its food. 
Of all sea birds, the frigate bird is one of the 
most remarkable. [Its flight is not as distant from 
shore as that of the albatross, but it is equally of 
great duration, the bird having extraordinary length 
of wing in addition to the special organs for giving 
