that connect the Orders and Families of Birds. 419 
Tachypetes, Vieill., we find a still more immediate approach to 
the Birds of Prey*, in their raptorial habits, their soaring and 
aerial flight, and the rapid seizure of their prey without im- 
mersing themselves in the waters whence they seek it. The last- 
mentioned genus, T'achypetes, in particular, exhibits in its general 
habits and structure the most conclusive evidence of this affinity, 
and of its deviation at the same time from the Natatores. Al- 
though for the most part it pursues its habits of rapine atimmea- 
surable distances from the shore, and derives its support exclu- 
sively from the ocean, it is never known to rest upon its surface. 
It does not possess in fact, to a sufficient extent, those glands 
which by their oily secretions preserve the plumage of other 
oceanic birds from the effects of the water; while the extreme 
disproportion of: its hinder extremities deprives it of the power 
of either swimming* or walking. On observing the structure of 
its legs we immediately detect this deficiency. Short, weak, 
and feathered down to the toes, they are equally unsuited to the 
land and the water. Its powers of motion and the characters by 
which it maintains its station in nature are in fact centered in 
its wings. Supported in its unlimited flights by the strength 
and expansion of these members, and aided by the singular me- 
chanism of its tail and the buoyant nature of the inflated sac 
which distends its throat, it seems to be an inhabitant of the air, 
rather than of the land where it resorts alone for the duties of its 
nest, or of the water over which it only hovers forits prey. These 
extraordinary and strongly marked characters, by which it thus 
appears as it were to fluctuate between the confines of the two 
* Fregata avis Oculi nigri, acie acutissimá et Aquilinä.— Pedes breves ; ungues 
Vulturini.—A ramis arborum in quibus resident difficulter admodum se levant: ve- 
rum cum semel in sublime evolárunt, motu placido absque ullà fere alarum agitatione 
aérem tranantes videas velut fluxu aut lapsu quodam, ad instar Milvorum.— Raii Syn. 
+ See Linnean Transactions, vol. xiii. p. 3. 
p. 153. 
VOL. XIV. 3t orders 
