CETACEA. 767 
arterial blood in different parts of the body, may be asso- 
ciated with the aquatic life. 
The cervical vertebree are thin, and more or less fused. 
There is no union of vertebree to form a sacrum, for the 
Fic. 412.—Left fore-limb of Fic. 413.—Fore-limb 
Balenoptera. of whale (A/egaptera 
Sce., Scapula with spine (s4.); 4, longimana).—After 
humerus; #., radius; U., ulna; Struthers. , 
C., carpals embedded in matrix ; 
Mc., metacarpals; PA., phal- 
anges. 
hind-limbs are at most very rudimentary. Under the 
caudal vertebre there are wedge-shaped chevron bones. 
The brain-case is almost spherical; the supraoccipital 
meets the frontals and shuts out the parietals from the roof 
of the skull; the frontals arch over the orbit; the snout or 
rostrum of the skull is composed of premaxillz, maxillz, 
