ir. VERTEBRATA: MAMMALIA, CAIiNIVOltA. 647 



structure of teeth and claws. Since this i)redaceous character in- 

 creases within the order from the bears to the cats, and again tends 

 to disappear in tlie aquatic species, there are few constant charac- 

 ters, hut a great variation in structure. In interest of greater 

 niobility tlie chivicle is reduced or lost, ulna and radius well de- 

 veloped. In the structure of the feet there is a gradual transition 

 from the plantigrade bears, \n which the whole solo of hand and 

 foot rest upon the ground, to the digitigrade cats, which tread on 

 the tips of the toes. In the latter the claws, which occur in all 

 carnivores, are kept from injury, when not in use, by being re- 

 tracted by an elastic ligament into pockets on the penult joint, 

 from which they are extended by strong muscles. lu dentition 

 ( g. 050) the striking features are the almost constantly three 

 incisors, and the great size of the canines; the molars, on the other 

 hand, vary with the different families, the cusps assuming more of 

 the shearing character (secodont teeth). The last premolar of the 

 ui^per jaw and the first molar of the lower jaw become carnassial 

 teeth (sectorial teeth), and acquire a dominating position in the 

 jaw, while the others ])ecome smaller and tend to disappear at 

 either end of the series. Further characters are the possession of 

 a penis bone in the males, the abdominal position of the milk 

 fdands and the uterus bicornis in the females; the ijlacenta is 

 zonary. Anal glands, furnishing a strong, even offensive smelling 

 secretion, are of wide occurrence. 



Sub Order I. FISSIPEDIA. Tlieso are the typical members of tlie 

 order and are preeminently terrestri.il animals with well-developed toes 

 usually cleft to the base. The number of digits is frequently five on all 

 feet, but is often reduced to four on the hind feet (Felidse, Canida^j, rarely 

 on the fore feet (Hya^nidse); but in these cases, as in the domestic dog, the 

 reduced first too may bear a claw, Ursu)^, plantigrade; Ursus* bears; 

 Proojon lotor* raccoon. Mustelid^; many species of. Mustela * and Piito- 

 rius,*- which include minks, martens, sable, ermines, and weasels, are 

 valuable for their fur; i((;/'a,* otter ; Enhijdris* sea otter; Mepldtis;* 

 skunk; Taxidea* badger ; Oulo* glutton ; anal glands common in this 

 family. Fossils (Ardotherium, etc.) connect the bears and the Ca.nid^ 

 with five toes in front, four behind, claws not retractile; which includes 

 in the genus Canis* dogs, foxes, and wolves. The Felid^ have toes as in 

 the dogs, but with retractile claws. Felis domeslica, our domestic cat. 

 F.Jeo, Hon; F. tigris, tiger; F. r-ijucolor* puma or cougar. Hy.enid.e, 

 all feet freer-toed; Hijmia of Africa. 



Sub Order II. PINNIPEDIA. These are aquatic carnivores with the 

 limbs flattened to broad flippers, the five toes long and webbed, the nails 

 frequently rudimentary ; the dentition differs from that of the terrestrial 

 foi-nis in the similarity of molars and premolars (absence of carnassial) ; 



