n8 



A BOOK OF WHALES 



developed in the Rorquals, where the whalebone is 

 shortest. 



The ribs are never attached to the vertebrae by 

 more than one head, which is the tubercular head, 

 i.e., that articulating with the transverse process of 

 the vertebrae. The sternum is always in one piece, 

 and only a single pair of ribs articulate with it. It 



FIG. 19. Skull of Balccna australis, dorsal view. 

 (From van Beneden and Gervais.) 



SO, Supra occipital. P, Parietal. F, Frontal. N, Nasal. 



(N.B., the left nasal is represented as absent.) 



MX, Maxilla. PMX, Premaxilla. 



is always very small in proportion to the size of the 

 body and does not represent a fused sternum of several 

 segments, but the manubrium only. 



It is usual, perhaps, to divide the Mystacoceti into 

 two families : the Balaenidae and the Balsenopteridae, 

 This arrangement is that followed by Gray in his 

 Catalogue. It is the arrangement found in many text- 



