142 ANDREW JACKSON HOWE. 



break the shock by means of a well developed plantar 

 arch and elastic plantar ligaments which stretch from 

 heel to toe as a cord subtends a bow. The tracks of 

 the kangaroo are much like those of a hopping bird. 

 The bandicoot has a hind foot similar to that of the 

 kangaroo, yet the "little" or outside toe is compara- 

 tively dwarfed, and the one next to it is as much more 

 enlarged and elongated it becomes the greater part 

 of the foot, while the others dwindle to insignificance. 



In the fore foot of the rnole there is seemingly a 

 violation of the pentadactyl type, for six terminal 

 claws are found. But upon dissecting the limb it is 

 shown that the supernumerary claw is a falciform 

 hook that springs from the radius, and is not there- 

 fore carpal except in function a splint to give width 

 and strength to the spade-like hand. 



The sloth has but two toes functionally devel- 

 oped in front ; and two rudimentary digits exist, 

 yet the animal is called two-toed. The nails on the 

 developed digits are long, strong, and so curved that 

 when hooked upon the branch of a tree, they will 

 not let go, though the animal be asleep or even 

 dead. A species of the sloth has three toes in the 

 fore foot, and a rudimentary fourth. The jerboa has 

 three toes to each hind foot, and three ankylosed 

 metatarsal bones. The conformation of the entire 

 limb is much like that of a bird. 



The anterior extremity of the bat has four enor- 

 mously extended phalanges to give expanse to skinny 

 wings ; the fifth digit is only a hook or undeveloped 

 claw. The posterior extremities present five digits to 

 each foot; thus, in the anterior arid posterior extrem- 

 ities, the pentadactyl type is followed. 



