THE BALiENOIDEA. 



337 



a. In the ^alcenoidea the nasal chambers communicate 

 with the exterior by two apertures, which are capable of being 

 shut at the will of the animal, and are called spiracles. These 

 are not connected with any saccular dilatations of the nasal 

 passages, situated between the skull and the integument. 



In the spinal column, no rib has a complete neck and capi- 

 tulum, the heads of even the most anterior ribs being united 



IV' 



so 



J>m!T 



Pis. 104.— Lateral and superior views of the skull of a foetal Whale {Balrvna AusfralisX^ 

 The.jugal bones are absent, and the figure does not sufficiently indicate the outwai-d 

 curvature of the ramus of the mandible (Jtfn.), 



15 



