ANA TOMY OF BIRDS 249 



a rudiment ; the ceratobrancliials are long, and the epibranchials so 

 extraordinarily elongated in some species as to curl up over the back 

 of the skull and forward along the top of the skull to a variable 

 distance; sometimes, as in Fig. 73, curling around the orbit of the 

 eye, or, as in Fig. 74, running into the nostril to the tip of the beak. 

 In such cases they bundle together in passing forward over the 

 skull, and go obliquely to one side. 



Other Bones of the Skull. — The articulation of the lower jaw 

 Avith the quadrate may have certain sesamoids. Thus, there are two 

 such sderosteous or ligament-bones in the external lateral ligament 

 of the raven's jaw-joint, and the long occipital style of the cor- 

 morant and snake-bird is of the same character, being an ossification 

 in the nuchal ligament of the neck. The siphon-like tube which 

 conveys air from the outer ear-passage to the hollow of the mandible 

 may ossify, as it does in an old raven, for example, resulting in a 

 neat tubular " air-bone " or atmosteon (Gr. ar/xo?, air). 



Types of Palatal Structure. — The arrangement of the bones of 

 the palate in birds results in several tj^pes of structure, first defined 

 by Huxley and applied to the classification of birds. These are the 

 dromceognathous, schizognathous, desmognathous, and cegithognatlious ; to 

 which Parker has added the saurogncdhous. Huxley proposed to 

 make the primary division of Carinate birds upon this score ; and 

 since the plan could not be made to work in his hands, it is certainly 

 futile for any one else to demonstrate again the impossibility of 

 establishing the higher groups of birds upon any one set of charac- 

 ters, — upon the modifications of any one structure. Nevertheless, 

 when duly co-ordinated with other characters, palatal structure 

 becomes of the utmost importance in defining large groups of birds. 

 It is necessary, therefore, for the student to clearly understand this 

 matter, which I Avill lay before him as nearly as possible in the words 

 of the authors just mentioned. 



Dromseognathism (Gr. Spo/xato?, dromaios, a runner : genus-name 

 of the emeu). All the Eatite birds, and the tinamous alone of 

 Carinate birds, are dromceognathous. " The posterior ends of the 

 palatines and the anterior ends of the pterygoids are very imperfectly, 

 or not at all, articulated with the basisphenoidal rostrum, being 

 usually separated from it, and supported by the broad, cleft, hinder 

 end of the vomer. Strong basipterygoid processes, arising from the 

 body of the basisphenoid, and not from the rostrum, articulate with 

 facets which are situated nearer the posterior than the anterior ends 

 of the inner edges of the pterygoid bones." This is the gist of 

 dromceognatlmm ; it is exhibited in several ways, (a) In Siruthio 

 alone. Fig, 75, the very short vomer, borne upon the rostrum, articu- 

 lates neither with palatines nor with pterygoids, but with the maxillo- 

 palatines ; and the palatines, which are remote from the rostrum. 



