410 



METAZOAN PHYLA 



the pinna, characterize the ear of the mammals (Fig. 221). 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 

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

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



-Olfacfory 

 bulb 



Cerebrum 



Cerebelfum 



Fig. 280. — Brain of European rabbit, Lepus cnniculus Linnaeus, seen from the side. 

 {From a Ziegler model, after Wiedersheim.) The roots of the cranial nerves are marked by 

 roman numerals. 



highly developed sense of smell, the sensory olfactory membrane being 

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

 sense of taste is also well-developed, taste buds being collected in certain 

 areas on the tongue. 



438. Classification. — Mammaha may be subdivided as follows: 



CLASS MAMMALIA 



Subclass L Prototheria (pro tothe'rl a; G., protos, first, and therion, mammal). — 

 Egg-laying mammals. 

 Order 1. Monotremata. 



