428 



METAZOAN PHYLA 



the pinna, characterize the ear of the mammals (Fig. 234). These 

 bones are the malleus, incus, and stapes. Of these the malleus corresponds 

 to the articular bone in the lower jaw of reptiles and birds and the incus 



Carotid artery 

 Vugular vein 



Pulmonary 

 artery and 

 vein 



Aortic arch 



SubclayJan 

 artery and 

 vein 



fiepatic 

 portal 

 system 

 Vena caycj 



Iliac 

 artery 

 and vein 



/Mesenteric 

 vessels to 

 intestine 



Fig. 319.— Diagram of mammalian circulation. Vessels carrying venous blood, black; 



arterial blood, white. 



to the quadrate, the stapes having been present from the amphibians 

 onward. The sense of hearing is very acute. Mammals possess a 

 highly developed sense of smell, the sensory olfactory membrane being 

 spread over the upper and lateral walls of the nasal chambers. The 



