100 



Elementary Zoology. 



anterior, and much the shorter one, represents the lower bit of 

 the hyoid arch, while the posterior long and upwardly curved 

 rods are the first branchial arch. The fowl is thus considerably 

 further away from the primitive fish-like condition than is the 

 frog, where there are remains of three purely branchial arches. 



The general plan of the bird's skull is shown in Fig. 43, 

 where the bones are represented diagrammatically, and in their 

 approximate positions, but disarticulated. As with the figures 



z.s. f;A. o.f: 



F.M. B.O. B.S. Ptfl.S. RL. ".N. 



Fjg. 44 — Skull of Rabbit. (For lettering, see text.) 



of the frog's skull above, the membrane bones are dotted. 

 The cartilage bones are left white. 



The skull of the Rabbit ofiers a number of differences in 

 structure from that of the bird. The most important of these 

 are the following : — 



1. The skull articulates with the atlas by two instead of by 

 one occipital condyle. 



2. The basitemporals are absent. 



3. The representative of the quadrate is a small bone within 

 the ear, the malleus.^ 



' It must be borne in mind that this is only one view out of many. 

 Some regard the articular surface of the squamosal as the quadrate, others 

 the tympanies. 



