DIVISIONS OF MAMMALIA. 525 



Order V. Cetacea, comprising the true Whales and Dolphins, 

 characterised by being aquatic Mammals, with a horizontal 

 tail-fin, no sacrum nor hind-limbs, and fore-limbs in the form 

 of swimming-paddles. The nostrils are single or double, and 

 are placed on the top of the head. The mammary glands are 

 two in number, and are placed in the region of the groin. 

 There is never more than one set of teeth, and in many cases 

 the adult is destitute of teeth altogether. Placenta non-de- 

 ciduate. 



Order VI. Ungulata or Hoofed Quadrupeds, comprising the 

 whole of the Ruminants, the Horses, and most of the old 

 group of the Pachydermatous Mammals. This order is split 

 up into many important sections, and, as a whole^ it is simply 

 characterised by the fact that there are never more than four 

 full-sized toes to each limb, and that the extremities of the toes 

 are furnished with expanded nails, constituting hoofs. There 

 are no clavicles. Placenta non-deciduate. 



Order VII. Hyracoidea, comprising only the single genus 

 Hyrax, characterised by having no canines, but by having 

 long curved incisors, which grow from permanent pulps, as in 

 the Rodents. There are no clavicles. The front-feet have 

 four toes, and, the hind-feet three. The placenta is deciduate 

 and zonary. 



Order VIII. Proboscidea, comprising no other living Mam- 

 mal except the Elephant, characterised by haying no canines, 

 but only molars and incisors, of which the latter grow from 

 permanent pulps, and constitute defensive tusks. There are 

 no clavicles. The feet are five-toed. The nose is prolonged 

 into a proboscis. The mammae are two in number. The 

 placenta is deciduate and zonary. 



Order IX. Carwiwra, comprising all the well-known beasts 

 of prey, such as Lions, Tigers, Dogs, Cats, &c., together with 

 the aquatic Seals and Walruses. They are all characterised by 

 always possessing the three different kinds of teeth — ^incisors, 

 canines, and molars — the canines being usually of great length, 

 and a greater or less number of the molars having sharp cut- 

 ting edges. The clavicles are always rudimentary, the teats 

 are abdominal, and the placenta is deciduate and zonary. 



Order X. Eodentia, comprising the Beavers, Rats, Mice, 

 Hares, Rabbits, Squirrels, and others, characterised by the 

 absence of canines and the possession of no more than two 

 incisors in the lower jaw, and usually no more than two in the 

 upper jaw. The incisors are greatly developed, growing from 

 permanent pulps, and continuing to grow during the life of the 

 animal. . Placenta deciduate and discoidal. 



