IHE OKDEka. 



59 



a representative. Here is a " Schizogna- 

 thous" skull, that of the Crane, with 

 the lower half removed so as to show 

 the arrangement of the bones we want. 

 Here quad, is the quadrate bone on 

 which the lower jaw works ; jtter. is 

 the pterygoid ; pal. is the palatine ; max. 

 pal. is the maxillo-palatine ; premax. is 

 the premaxillary, and vomer is the vomer, 

 the bone which is the key to the classifica- 

 tion, and which varies more than almost 

 any other bone in the skull of a bird. It is 

 a small bone, thin as a knife blade and 

 rarely broader, standing on its edge in the 

 very centre of the roof of the bird's mouth, 

 a bone so delicate that it is one of the 

 first to vanish when the student in search 

 of it first prepares a skull. It will be 

 noticed that in the case of the Crane it 

 ends in a point towards the beak, and it 

 so ends in the skulls of Plovers, Gulls, 

 Fowls, and Pigeons, and others. In this 

 group, we may as well quote as paraphrase, 

 " the maxillo-palatines are usually elon- 

 gated and lamellar ; they pass in-<vards 

 over the anterior processes of the palatine 

 bones, with which they become united, and then bending backwards, 

 along the inner edge of the palatines, leave a broader or a narrower 

 fissure between themselves and the vomer, and do not unite with it or 

 with one another." 

 But in the skulls of the Passerine birds the vomer is not pointed 

 in front. Here, for instance, is the skull 

 of a Raven, one of the Passerines. 

 It is " .(Egithognathous," with the 

 maxillo-palatines free, and the vomer 

 unpointed, or rather cut off at a blunt 

 angle. The lettering is as before, but 

 owing to the more open character of 

 the skull the parts are more clearly 

 traceable. Again, the quadrates lead on 

 to the pterygoids which lead on to the 

 palatines, and in the centre of the 

 palatal framework we see the thin edge 

 of the vomer. It will be seen that in 

 this skull, as in that of the Crane, the 

 maxillo-palatines are clearly separate. 

 The vomer in this group is cleft behind, 

 embracing the rostrum of the sphenoid 

 between its forks. "The palatines have 

 postero-external angles. The maxillo- 

 palatines are slender at their origin, and 

 extend inwards and backwards obliquely 

 over the palatines, ending beneath the 

 E 2 



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