148 STRUCTURE AND CLASSIFICATION OF BIRDS 



The degree of development of the lacnjmals and the 

 ectethmoid processes varies greatly among birds, and is at 

 times of use for systematic purposes. In some birds, as, for 

 example, among the cranes, there is no junction between 

 those bones ; in the Charadriidge, on the other hand they 

 form a complete ring ; in Pterocles, &c., the two are firmly 

 blended into a square plate of bone which bounds the orbit 

 anteriorly. 



The lacrymal is occasionally joined to the palatine or to 

 the jugal by a small independent ossicle, which PARKER has 

 termed the uncinate bone, and thinks to be the homologue 

 of the anterior connection of the palato-quadrate arch with 

 the skull in the tadpole, &c. This bone is so variable in its 

 presence (e.g. Cariama, Tubinares) that it can hardly be 

 regarded as of much systematic importance. The last matter 

 to which we may refer as of classificatory importance is the 

 form of the quadrate, which Miss WALKER has shown to 

 vary much and characteristically in different groups. It had 

 been long known that the single-headed articulation with 

 the skull was a character of struthious birds, excepting 

 Apteryx, and of Ichthyoniis, and to a less extent of gallina- 

 ceous birds and ducks. 



The value of the base of the skull in classification has 

 been continuously debated since the facts were first so clearly 

 set forth by HUXLEY. 



From the complications introduced into the originally 

 simple series of modifications of the skull instituted by 

 HUXLEY, by PARKER, and from the varied criticisms of fact 

 and conclusion of a classificatory kind based upon fact, we 

 may disentangle one conclusion that many ornithologists 

 will agree with that is, the more lacertilian character of 

 the skull in the struthious than in other birds. In them the 

 palatines are borne off from the basisphenoidal rostrum by 

 the vomer (with the exception of Strutliio, in which, however, 

 the palatines are still remote from the rostrum), and the 

 general disposition of these parts is, as HUXLEY wrote, 'more 

 lacertilian than in other birds.' Furthermore in the stru- 

 thious birds the double character of the vomer is more 



