MAMMALIA. 313 



of Olis, Rallus, and Crcx, in diluvian deposits with the pre- 

 ceding genera. 



7th Order. NAT.ATORES (or Swimmers). To this group 

 belong the extinct genus Cimoliornis, from the wealden of 

 Kent, and the extinct species of Carbo, from the eocene of 

 Montmartre. The same genus with Mergus and J^s are 

 found in the sub-apennine of Auvergne ; and Larus^Anser, 

 and Colymlus, in the diluvium of caverns. 



CLASS IT. MAMMALIA. 



THIS class includes man, and all the higher quadrupeds 

 that nourish their offspring during the first months of their 

 life with a nutritious secretion or milk, furnished by two or 

 more mamma?, or milk glands. Their skeleton presents 

 important modifications of structure, which serve for the 

 distribution of the class into many natural orders. 



The skull is composed of three vertebrae, the elements of 

 which are greatly developed and expanded to form the cranium. 



The first is the occipital ; the second the sphenoid with the 

 two parietal ; the third the ethmoid with the two frontal. 

 The face is formed of the two upper maxillary, and two 

 inter-maxillary, two palate, and two nasal bones, &c., &c. 

 The six first bones form the upper jaw. The lower jaw is 

 formed of two branches united at the median line, and 

 articulated by two condyles to the glenoid cavities of the 

 temporal bones, without any intermediate tympanic bones, as 

 in the oviparous vertebrata. 



The spinal vertebrae are divided into cervical, dorsal, lum- 

 lar, sacral, and caudal, as they are situated in the neck, 

 back, loins, sacrum or tail. The neck is always formed of 

 seven vertebrae ; the number in all the other regions varies 

 much. The number of those in the dorsal region corresponds 

 with the number of the ribs. These bones are united before 

 to a sternum, formed of a series of small bones, disposed in a 

 line and united end to end. The anterior extremities are 

 formed of scapula, or blade-bones, suspended by muscles alone 

 or connected with the sternum by clavicles, or collar-bones. 



