that connect the Orders and Families of Birds. 497 
before us directs us at once to the typical families of the present 
order. The groups that are most truly oceanic will be those which 
exhibit the greatest deficiency in their powers of flight and of 
motion on land. Thus in the typical Natatores, the backward 
position of the legs, which are thrown entirely behind the equili- 
brium of their body, almost totally deprives them of the faculty of 
walking; while their wings, considerably shorter, and less covered 
with feathers than those of any other birds whatever, bespeak 
their incapacity of maintaining a constant or sustained flight. On 
the other hand, these birds exhibit a superiority in the powers 
which contribute to their support in their own peculiar element. 
The feet, which by their position and structure are not calculated 
for the usual offices which these members perform on land, are 
admirably adapted to the purposes, more appropriate to the 
Natatores, of swimming and diving. In the same way the wings, 
which serve as feeble supporters in their progress through the air, 
answer admirably as fins to facilitate their movements in the 
water. 'lhose birds then will form the typical groups of the pre- 
sent order, which, like the Colymbus and A/ca of Linnæus, have 
short and slightly-feathered wings, and whose legs are so far 
thrown backward as to give them an almost erect appearance 
when on the ground. They will be found to be constant inhabi- 
tants of the ocean ; and although in some instances, as the Apte- 
nodytes of Linnæus, they are deprived of the powers of locomotion 
common to other birds, by the deficiency of their wings, they may 
yet pursue their prey at considerable distances from land. To 
such situations they must of course be conveyed by their superior 
powers in swimming. The aberrant groups, on the other hand, 
will be those where the powers of the wings are more considerably 
developed, and where the legs, thrown more forward, enable them 
to walk with comparative ease. "They thus appear in general to 
come more near the land-birds than the typical families of the 
order. 
