SEC. IV 



ANATOMY OF. BIRDS 



253 



and the latter is slender and usually pointed. There are plenty of 

 other birds in which the former factor in the case obtains ; but in 

 these the vomer is broad and usually truncate in front (see ^gifho- 

 gnathism, beyond). 



fPmap ^ 



^Mcp 



2te, 



Desmogrnathism (Gr. Sea-fws, 

 desmos, a bond) is exhibited in 

 one or another style by those 

 swimming and Trading birds 

 which are not schizognathous, 

 by the birds of prey, and 

 various non-passerine perching 

 birds. It does not fadge so 

 well as any other one of the 

 palatal types of structure with 

 recognised groups of birds 

 based on other considerations. 

 In this " bound-palate " type 

 the vomer is either abortive or 

 so small that it disappears; 

 when existing it is usually 

 slender and tapers to a point 

 in front; the maxillopalatines 

 are united across the median 

 line, either directly or by means 

 of ossifications in the nasal sep- 

 tum ; the posterior ends of the 

 palatines and the anterior ends 

 of the pterygoids articulate 

 directly with the rostrum (as in 

 schizognathism). This type is 

 simply and perfectly exhibited 

 by a duck (Fig. 78) in which 

 the maxillopalatine is a broad 

 flat plate united with its fellow 

 in mid-line ; the oval sessile 

 basipterygoid facets are far for- 

 ward, opposite the very ends 

 of the pterygoids. In the 

 flamingo, ibis, spoon-bill, stork, 

 heron, the united maxUlo- 

 palatines are tumid and spongy, filling the base of the beak ; 

 basipterygoids are wanting (rudimentary in the flamingo). In 

 totipalmate swimmers (pelican, cormorant), desmognathism is carried 

 to an extreme by union of the palate bones also across the mid-line ; 

 the general arrangement is as before. The birds of prey exhibit 



:pf.. 



Fig. 78. — De^mognathous skull of mallard 

 duck, Anas ioseas, nat. size ; from nature by Dr. 

 R. W. Sliufeldt, U.S.A. Letters as before. 



