NATATORES. 255 



they breed (Resident birds; Eagles, Owls, Ravens, Woodpeckers, 

 Magpies, Sparrows, Titmice, Grouse, etc.) Many of them rove over 

 larger and smaller regions in search of food ( Strichvogel ; Thrushes, 

 Bramblings, and Chaffinches, Woodpeckers, Yellow Bunting, Finches, 

 and crested Lark). Others migrate before the beginning of the cold 

 season of the year, when nourishment is deficient, from the northern 

 climates to the temperate, from these to southern regions (Zugvdgel : 

 Swallows, Storks, Jackdaws, Crows, Starlings, Wildgeese, Cranes, 

 etc.) 



There are but scanty materials for the geological history of this 

 class. Leaving out of consideration the feather-tailed Archceopteryx 

 lithographica* (fig. 119) of the Jura (Saururce), the oldest remains 

 of the swimming and wading birds belong to the chalk. In the 

 tertiary period the remains are indeed more frequent, but are never- 

 theless insufficient for a more accurate definition. In the Diluvium, 

 on the other hand, numerous types of species still living are found, as 

 well as remarkable gigantic forms which have become extinct within 

 the historical period (Palceornis, Dinornis, Palapteryx, Didus). 



I. CARINAT^!. 



The sternum has a keel (carina) for the insertion of the power- 

 fully developea v muscles of flight. The remiges of the wing and the 

 rectrices of the tail are usually well developed. Almost all are able 

 to fly. 



Order 1. NATATORES (SWIMMING BIRDS), 



Aquatic Birds with short legs often placed far back ; feet either pedes 

 palmati or p. stegani. 



The form of the body of the swimming Birds varies extraordinarily, 

 according to the special adaptation to their aquatic habitat. They sill 

 have a thick compact plumage, a very rich clothing of down, and a 

 large uropygial gland. The legs are short and are placed far back, 

 and usually feathered as far as the ankle. They end with swimming 

 feet, either pedes pcdmati, orjissipalmati, or stegani. The Nata tores 

 are all excellent swimmers ; many are strong flyers, while others are 



* This group, which is allied to the reptilian genus Gompsognatus (Ornitho- 

 scelida) is especially characterised by the fact that the caudal part of the 

 vertebral column is as long as the body, and was furnished with feathers, 

 arranged in pairs. Since the metatarsal bones are not fused, there is no true 

 avian tarsometatarsus. 



