418 NATATORES. ALCADM. 



comprising the Guillemots (Genus Uria), Auks (Genus AL 

 r), Penguins (Genus Aptenodytes}, and other nearly allied 

 groups, forms a second typical division of the Order Nata- 

 torcs. The greater part of the Alcadce are distinguished by 

 having only three palmated toes, and where a fourth or hind 

 toe does exist, it is very small, and without a membrane ; 

 and also directed forwards, as in Pelecanidce, thus leading the 

 way to the connexion of the present with that aberrant fa- 

 mily. We also find in them the shortness of wing, and con- 

 sequent deficiency in power of flight (which seems in general 

 most prevalent as aquatic habits become most decided), car- 

 ried to the greatest extreme ; the wings of the Penguins, and 

 other nearly allied genera, being so short and imperfectly de- 

 veloped, as to be totally unfit for the purpose of flight, and 

 adapted to act merely as fins, in aiding their progress be- 

 neath the water. As in the Cotymbida, the legs of the birds 

 of this family are placed far backwards, but at scarcely so 

 great an angle with the body as in the former, in consequence 

 of which they are enabled to sit in an upright attitude, rest- 

 ing equally on the foot and the whole length of the tarsus. 

 They are all attached to the ocean, never resorting to fresh 

 water, like the Cotymbi. Many of the species that are able 

 to fly, nestle on rocks and precipices, where they lay a single 

 egg, of a conical form, a shape which prevents it from rolling 

 away or moving (except within a circle of the diameter of its 

 own length), on the bare rock where it is deposited. Some 

 burrow in the light sandy soils of the small islands they fre- 

 quent ; and the Penguins, and other species, that have not 

 the power of flight, incubate upon the shore immediately 

 above high-water mark. The bill has a variety of form in 

 the different genera, but commonly much compressed, and 

 often grooved on its sides ; exhibiting through all its modi- 

 fications a beautiful illustration of the progressive series of 

 affinities that unite the members with each other. The food 

 of this family consists of fish, crustaceae, and other marine 

 animal productions. 



