XIII 



PHYLUM CHORDATA 



517 



S ft 



;~ 9 



8*2 

 ..j__-ft 



CO) ,; 



> S 03 



O . 



.o- 



35 I 





C ^" O 



E if 



S 



03 o 



o o i 



ftg 



o"^^ 

 ''- ^ ;? 



manus is extremely modified. 

 There are no synovial joints ; 

 the carpus is in some (Whalebone 

 Whales) almost entirely car- 

 tilaginous, as also are the 

 metacarpals and phalanges the 

 cartilages being coalescent or 

 separated by intervals of fibrous 

 tissue : in some of the carpal 

 elements bone is deposited. In 

 the toothed Whales the carpals 

 are completely ossified, and 

 are of polygonal form : the 

 phalanges are also ossified, with 

 incomplete synovial articula- 

 tions. In the Cetacea there are 



b ft >a 



~"ft 



feis, 



^ FIG. 1161. Sternum of Rorqual (Balccnop 

 K . tera musculus). (After Flower.) 



sometimes five digits, sometimes 

 only four : more or fewer have 

 considerably more than the 

 normal number of phalanges 

 sometimes as many as fourteen. 

 The second digit is usually the 

 longest. 



Vestiges of the pelvis are 

 present in the form of a pair of 

 long narrow bones (Fig. 1160, 

 pelv.) which lie parallel with the 

 spinal column some little dis- 

 tance below the region where 

 the chevron bones begin : these 

 appear to represent the ischia. 

 A second pair of smaller bones 

 which lie close to these in the 



".2 )* 



- 13 



o 

 S 



ftO 



