402 STRUCTURE AND CLASSIFICATION OF BIRDS 



(2) Scale-like feathering of the flattened wing. 



(3) Absence of biceps brachii muscle. 



(4) Presence of a vascular rate in the wing. 



(5) Freedom of cranial bones (not so marked in Eatitse). 



(7) Large and flattened scapula. 



(8) Short and imperfectly fused metatarsals. 



The opisthocoelous character of the lumbar vertebrae is 

 more pronounced than in other birds, but is, as has been 

 already said, a character found in many groups. 



These features, some of them, have appeared so important 

 to Mbnzbieb that he has divided birds into four great 

 groups — Sa,urur8e, Eatitse, Odontormse, Carinatse, and, finally, 

 the Eupodomithes or penguins. This, however, seems to be 

 a too great separation from other birds. Gadow would 

 place them nearest to the Tubinares and Steganopodes, the 

 Colymbi being only a little further removed. 



STEGANOPODES 



Definition. — AU four toes webbed.' Oil gland tufted; aquiuoubital. 

 Skull desmognathous, holorhinal, -witliout basipterygoid pro- 

 cesses.'' CsBoa present, but small. 



Though this group shows much divergency of structure, 

 its naturalness can hardly be doubted. The number of 

 rectrices varies. In Phalacrocorax hrasiliensis and graculus 

 there are twelve, so also in Fregata aquila and Plotus 

 anhinga.'^ Phaeton has twelve or sixteen. P. carbo has four- 

 teen. Pelecanus has up to twenty and twenty-four. 



The aftershaft is minute but distinct in Fregata, appa- 

 rently absent in Plotus and other genera. 



The skin is only slightly pneumatic in Fregata, not so at 

 all in Plotus. It is distinctly emphysematous in Phaeton,'^ 

 Pelecanus. 



' This one feature is sufficient to define the group. 

 ' Eudiments exist in Pelecwnus ; cf. infra, p. 409. 

 ^ P. melanogaster appears to have only ten. 



' Some few details of the structure of the soft parts of this tern-like 

 steganopod are to be found in Bkandt, ' Monographia Phaethoutum,' Mem. Ac 



