532 



ZOOLOGY 



SECT. 



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number articulate with botli 

 transverse processes and bodies 

 by distinct tubercles and heads. 

 The sternum varies in shape. 

 Sometimes it consists of a jore- 

 sternum and a series of several 

 sternebrae without xiphister- 

 num; sometimes (Fig. 1149) it 



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Fig. 114y.— sternum of Rorqual (5a/(t«o;>to-a 

 musadus)- (After flower.) 



is a continuous plate of bone, 

 occasionally with median notches 

 or fontanelles. 



In the skull (Fig. 1150), the 

 brain-case is rounded, the jaws 

 greatly elougated, often unsym- 

 metrical. The parietal s (Pa) do 

 not meet in the middle line 

 above in most Cetacea, being 

 separated by the supraoccipital 

 (SO.) and an interparietal (IP.); 

 there is thus no sagittal suture. 

 A large supra-orbital plate is 

 developed from the frontal. 

 There are large and stout zygo- 

 matic processes of the squamosal, 

 but the jugals are extremely 

 small. In all the recent forms 

 the maxilla (Mx.) is very large 

 and extends backwards to over- 

 lap a good deal of the frontal, 

 and forwards nearly to the ex- 

 tremity of the snout ; while the 

 premaxillie (P. Mx.), which are 



