40i' STRUCTURE AND CLASSIFICATION OF BIRDS 



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



(3) Absence of biceps brachii muscle. 



(4) Presence of a vascular rete 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 opisthoco3lous 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 MENZBIER that he has divided birds into four great 

 groups Saururas, Eatitse, Odontorma?, Carinatas, and, finally, 

 the Eupodornithes 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. All four toes webbed. 1 Oil gland tufted; aquincubital. 

 Skull desmognathous, holorhinal, without basipterygoid pro- 

 cesses. 2 Cseca present, but small. 



Though this group shows much divergency of structure, 

 its naturalness can hardly be doubted. The number of 

 rectrices varies. In Phalacrocora.v 6;v/.sv7/Vy/.s/.s and graculus 

 there are twelve, so also in Frcgata aquila and Plot UK 

 f lulling a? 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 Frcgata, 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. 



1 This one feature is sufficient to define the group. 

 '- Rudiments exist in Pelecanus ; cf. infra, p. 409. 



3 P. melanogaster appears to have only ten. 



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

 steganopod are to be found in BRANDT, ' Monographia Phaethontum,' Mem. Ac 



