//. TYPES IN DETAIL IVITH THEIR SUBORDINATE GROUPS. 49 



wanting; molars, when present, re- 

 semble those of ungulates. Sparsely- 

 hairy. A single pair of pectoral 

 mammary glands. Placenta in- 

 deciduate, diffuse. x Manalus. 



Order 5. Cetacea Aquatic forms with naked skin, pro- 

 vided with hair in embryo. Hind 

 limbs fail externally; rudiments 

 under skin. Mammary glands in 

 folds on the sides of the vagina. 

 External nares in top of head con- 

 necting directly with a tubular pro- 

 longation of the larynx. Placenta 

 indeciduate, diffuse. x Balana. 



Order 6. Artiodactyla Hoofed mammals with an even 



number of toes, of which two (3 

 and 4) are the best developed, re- 

 sulting typically in the cloven hoof. 

 The prag-molars, 3-4, are smaller 

 than the molars. Many members 

 of this Order are ruminants. Pla- 

 centa indeciduate, cotyledonal in 

 most ruminants, in other cases dif- 

 fuse. X Bos, Hippopotamus. 



Order 7. Perissodactyla Hoofed mammals with an odd 



number of toes, five, three or one, 

 the middle one being the best de- 

 veloped. Prae-molars equal the 

 molars in size. Integument often 

 very thick. Placenta indeciduate, 

 diffuse. X Rhinoceros, Equus. 



Order 8. Proboscidia A group allied to the two previous 



Orders, but with five stout toes 

 furnished with hoofs, making a 

 ponderous rounded foot. The 

 snout is enormously prolonged, 

 forming a muscular proboscis 



