NATATORES. STERNA. 461 
age, they float with much buoyancy ; but they make little 
use of their power of swimming, and are altogether incapa- 
ble of diving. Others, as the Petrels, never actually alight 
on the water, but use their webbed feet to run, as it were, 
upon the surface of the waves; and in this action they are 
assisted by their wings, which are kept partly open. The 
passage from the Pelecanide to these birds is effected by the 
near affinity existing between the genus Phaeton of that di- 
vision and the larger Terns which commence the present 
one. In this family also, according to the arrangement of 
Mr Vicors, a form is found connecting it with the Anatide, 
thus completing the circular succession of the Order ; and 
this he thinks is performed by Pachyptila, a genus nearly 
allied to the Petrels. The affinity thus endeavoured to be 
established, seems, I must confess, distant, and stands in 
need of the interposition of other forms to render it satisfac- 
tory and complete. 
Genus STERNA, Livny. TERN. 
GENERIC CHARACTERS. 
Brit as long as, or longer than, the head, almost strait, 
compressed, drawn to a fine point, with both mandibles of 
equal length, and the upper slightly convex. Tomia rather 
intracted and sharp-edged. Lower mandible having a pro- 
minent angle near its middle part. Nostrils basal, lateral, 
linear oblong, pervious. 
Wings very long, acuminate, soul the first quill-feather 
the longest. ‘Tail more or less forked. Legs having the 
tibiz naked for a short space above the tarsal joint. ‘Tarsi 
short. Feet of four toes, three before and one behind; the 
three front toes united by a membrane more or less scalloped, 
the hind toe small and free. Claws arched and sharp. 
The Terns, which, in the present family, appear to repre- 
