MAMMALS. 



407 



The teeth in existing species are homodont and monophyo- 

 dont, and never pierce the gums in the mystacocetes. In the 

 fossils there is evidence of descent from heterodont ancestors. 



Fig. 374. Skull of foetal cachelot whale {Physeter), from Huxley. AS, 

 alisphenoid; ^«, auditory region; j90, basioccipital ; ^.J, basisphenoid ; ^O, exoc- 

 cipital; ^/,4, ethmoid; /^?-, frontal; /«, jugal (displaced in the side view from its 

 connection with the squamosal) ; jKt, maxillary; TV, external nares; 7°a, parietal; 

 PI, palatine; Pmx, premaxillary; SO, supraoccipital; Sq, squamosal; Vo, vomer. 



The number varies greatly. The stomach (p. 367) is several 

 chambered, the intestine is comparatively simple, a caecum being 

 present in some species. The liver has four lobes, and no gall 



