oY 
The pelicans are seen of an evening retiring to 
their roost in the outer islets in pairs. . 
In every family of animals there is a prevailing 
character peculiar and definite, which is always 
predominant, whatever may be the differences of 
the several species which that family includes. 
Thus among birds, in the falconidz we perceive the 
essential trait to be the raptorial power of the talons, 
the special differences being an accommodation of 
the body to restricted habits and pursuits ; in the 
gallinaceze, the rasorial quality of the foot and its 
adaptation for defence; in the ardeadz the javelin 
properties of the bill for spearing the fish; and in: 
the anatide the sensitive power of the mandible 
formed in the shape of a spoon to enable the several 
individuals of the duck tribe, to examine and scoop 
up and search the waters for infusoriz and other 
animaleulz. The Pelicanide considered in this 
way exhibit as a predominant character a structure 
in the greatest possible degree adapted for changing 
the specific gravity of the body so as to accommo- 
date it to sudden and instantaneous transitions from 
heaviness, when rapidly descending upon a prey, 
to extreme buoyancy when pursuing it, added toa 
facility of lessening its specfic gravity, when bur- 
thened with a load of provender. 
In the pelicans, the lower jaw affords suspension 
to a capacious pouch in which the bird bears away 
a considerable weight of fish, but the corresponding 
sack about the neck and throat of the tachypetes, 
or frigate bird is simply a large reservoir for air, to 
