DIVISIONS OF THE VERTEBRATA. 339 



a single piece, and the lower jaw is united with the temporal 

 (squamosal) element of the skull, and is not articulated to a 

 quadrate bone. There are special glands the mammary 

 glands for the nourishment of the young for a longer or shorter 

 period after birth, and the red blood-corpuscles are non- 

 nucleated. 



