184 ON THE CLASSIFICATION OF BIRD‘ ¥ 
itions of cold and heat, As the ocean is their elen 
so do its waters supply their food: some live bo 
upon aquatic plants and submarine insects; but 1 
greatest proportion prey upon fish, and those inn nel 
able swimming and creeping things which subsist it 
the sea, and cover its shores, a 
(205. ) The lpr order has been divided into th 
- following families *, which have every appearance of 
being the natural primary divisions: —1. The Ducks 5 
(AnaTipz);—2. The Gulls (Lari) ; — 3. be 
Pelicans (PELicanipz) ;—4, The Penguins (Arc1 
pn#£);— 5. The Divers (Cotympip#). The three fir 
are distinguished by the length of the wings, which e 
able them to fly well; while, in the two latter, thes 
members are so short, ‘that they seem perfectly usele 
for any other purpose than to serve the office of fins. 
rapid survey of the prominent characters and groups of 
these families is all that can be here said of them. = 
(206.) The analogies of the primary groups of the 
natatorial order have never been made out, and they” 
are, in truth, involved in much difficulty; at least, if 
we are to judge from the trouble their investigation has” 
cost us. There can be no doubt, indeed, that the 
typical perfection of the order rests with those birds” 
whose structure is more especially adapted for diving 
and swimming; and it therefore follows, as the result 
of this conclusion, that the Colymbide, or divers, and 
the Alcida, or ee constitute the two primary types i 
the lengthened and conic bill of the first of these” 
families assimilates with that form belonging to the 
Conirostres ; and we may, therefore, safely infer that 
it represents that tribe. The Alcide, on the other 
hand, have a short and broad bill, considerably curved — 
on the culmen, where it is gradually arched from the 
base ; while the tip, although not toothed, is bent over 
the fetes mandible: this, in fact, is the general outline 
of the bill of dentirostral types, even in remote groups, — 
such as the Psittacide, among the Scansores ; and it iting 
* Vigors, Linn. Trans. xiv. 
