STEGANOPODES 419 



relationships of this remarkable fossil ; but the facts are at 

 any rate not opposed to that placing. 



Of birds more definitely referred to the Steg^anopodes a large 

 number have been described from Tertiary strata. If Mabsh's 

 G^-aculavus, from the Cretaceous, really belongs here, the group is 

 as old as any existing group, and older than most. Argillornis 

 {= Lithornis) of Owen is among the most interesting, inasmuch 

 as it is known from fuller remains than others. The skull and 

 some long bones have been found in the London clay. It is 

 referred to the neighbourhood of the present group by Lydbkkbk, 

 but by PuEBEiNGEE to the Ichthyornithes. 



Actiornis, Pelargornis are placed here by Lydekkee, and Pue- 

 BEiNGBE would include Bemiornis (considered struthious by 

 Gadow) and Ghenornis, referred by others to the Anseres. 



HERODIONES 



Definition. — Oil gland feathered." Aftershaft present.^ Aquinoubital. 

 Skull desmognathous, iolorliinal, ■with.out basipterygoid pro- 

 cesses. Oatapophysial canal nearly always present. Two 

 carotids. Caeca present, but nearly always rudimentary. Ex- 

 pansor secundariorum presenj. 



This group of birds is an extensive one, with a con- 

 siderable range of structural variation. That the flamingoes 

 form a group apart can hardly be doubted, though it is not 

 easy to differentiate them by any very important characters 

 from other Herodiones. Less easy is it to distinguish the 

 herons from the storks. The extreme types, e.g. Giconia 

 and Cancroma, can be readily distinguished by the muscle 

 formula and by the characters of the syrinx, not to mention 

 some other points of minor importance ; but between the 

 extremes are forms like Abdimia, Scopus, and Balceniceps, 

 which forbid so sharp a line of division. As to Phwni- 

 copterus, Wbldon was the first ^ to show in a convincing 

 way its likenesses to the stork, its previous association with 

 the duck tribe having been in large part due to the lamellated 

 bill and the webbed feet. As to the latter character, no one 



' Except in Cancroma. ' ? except in Leptoptilus argala. 



^ ' On some Points in the Anatomy of Phcenicopterus,' &c., P. Z. S. 1883, 

 p. 638. 



Id I. 2 



