272 AVES CLAS8IV 



and the ilium and ischium are always fused posteriorly. The hypotarsus has 

 oiie or more tendinal canals, and the sternum is generally keeled, although this 

 is a character of little value, since any group may have its flightless forms. 

 Thus we have the owl parrot (Stringops habroptilus), Harris's cormorant {Halieus 

 harrisi), the weka rail {Ocydromus australis), and the dodo (Didus ineptus), 

 each representing a difterent order. 



Limits of space preclude more than a brief survey of the various sub- 

 divisions of the Euornithes, and the student will no doubt be Struck by the 

 slight and often unsatisfactory nature of the osteological characters used to 

 define them. It is hoped that failure in this respect may be pardoned, since 

 Huxley, Fürbringer, and Beddard were all forced to rely largely on the muscles 

 and pterylosis to define their divisions of birds. 



Order 1. IMPENNBS. Penguins.i 



The penguins deserve particular notice on account of their high specialisa- 

 tion as swimming birds, while at the same time they present some primitive 

 characters. The wings are shortened, fiattened, and modified into paddles, but 

 as they are moved by the muscles employed by other birds in flight, the 

 sternum retains its keel. The skull is schizognathous, and the component 

 bones remain free from one another for an unusual length of time ; the 

 pterygoids are very large. The scapula is unique among birds in being 

 expanded posteriorly. The dorsal vertebrae are markedly opisthocoelous. 

 The tarsus is short and wide, and its three component tarsals plainly indicated 

 by their imperfect fusion. 



On account of these characters and peculiarities found in the pterylosis 

 and muscles, Gill, Stejneger, and Menzbier have considered the penguins as 

 forming a group equal in value to the rest of the Euornithes ; but this seems 

 too exalted a rank, and does not take purely adaptive features sufficiently into 

 account. The group is characteristic of the southern parts of the southern 

 hemisphere, but extends to the equator ofF the west coast of South America. 

 Its geological histor}^ is imperfectly known, but the penguins must have 

 attain ed their specialisation at an early date, as one genus (Palaeospheniscns) 

 has been obtained from the Eocene of Patagonia, and a giant form (Palce- 

 eudyptes) is known from the Eocene of New Zealand. 



Order 2. CBCOMORPHAE. 



The Cecoinorphae include the auks, gulls, divers, and petrels, these last 

 diverging from the other members of the order and often placed in an order 

 by themselves, the Tubinares. The divers {Colymbidae) and petrels are con- 

 sidered, among existing birds, to be those nearest the penguins, the Tubinares 

 again having some points of resemblance to the storks (Grallae). The Ceco- 

 morphae are swimming birds, having a schizognathous palate and the angle of 

 the mandible truncate. 



An albatross, Diomedea anglica, occurs in the Red Crag, Pliocene, of 

 England, and remains of gulls are numerous in the Miocene of the south of 



^ Watson, J/., Report ou the Penguins collectecl by tlie Challenger (Challenger Reports, vol. VlI. 

 Part XVIII.), 1883. 



