AS MEANS OF IDENTIFICATION 581 



2 FAMILY DIOMEDEID.E ALBATROSES. 



Supra-orbital groove, with a more or less extensive overhanging ledge, the free edge of 

 which is flattened ; temporal fossie represented by shallow semicircular depressions of 

 uniform depth, divided one from another by the broad, shield-shaped roof of the skull ; 

 nasal fossae almost completely closed ; external apertures of nostrils in the form of small 

 tubes lying in a groove on each side of the beak ; length of upper jaw greatly exceeding 

 that of the cranium ; palatines closely approximated in the middle line, so as nearly to 

 conceal the vomer ; palatines relatively short, and with ventral keels reaching down to 

 the level of the tomium ; wing very long and ribbon-shaped. 



(a) Genus Diomedea. Interorbital region of frontals very broad ; culmen concave ; 

 feathering at the base of the upper jaw extending forwards nearly to the base of 

 the nasal tube ; feathering of the lower jaw extending forwards nearly as far as 

 the level of the aperture of the nostril. (Vol. iv. p. 556.) 



X 



ORDER: COLYMBIFORMES 



Skull schizognathous ; nostrils holorhinal ; basipterygoid processes absent ; temporal fossa; 

 deep ; spina externa short, bifid ; spina interna wanting ; pelvis laterally compressed ; neck 

 pterylosis without apteria ; wing diastataxic ; young nidifugous. 



1. FAMILY COLYMBnXE (PODICIPEDID^E) GREBES. 



Supra-orbital grooves feebly developed, lachrymal free ; post-orbital processes obsolete ; 

 greatest width of sternum more than half, sometimes equal to, its length ; metasternum 

 deeply notched ; cnemial crest shorter than femur ; patella very large ; tarso-metatarsus 

 laterally compressed ; front toes lobed ; tail vestigial. 



(a) Genus Colymbus (Podicipes). Characters as for the family. (Vol. iv. p. 405.) 



2. FAMILY GAVIAE (COLYMBIDJE) DIVERS. 



Supra-orbital grooves very deep and with a well-developed ledge ; temporal fossae wide, and 

 separated by a median sagittal ridge ; lachrymal fused with nasal ; large post-orbital 

 processes ; cnemial process of tibio-tarsus rising high above the articular surface, longer 

 than the femur ; greatest width of sternum less half its length ; metasternum lingui- 

 forin ; tarso-metatarsus laterally compressed ; front toes webbed ; tail well developed 

 but short. 



(a) Genus Gavia (Colymbus). Characters as for the family. (Vol. iv. p. 435.) 



VOL. IV. 4E 



