322 THE HIND FOOT OR PES. [chap. 



The three middle toes have the usual number of bones, but 

 the terminal phalanges are small and irregular in shape. 

 The first and fifth toes have each one phalanx beyond the 

 metatarsal. The astragalus is very flat, and has no articu- 

 lation with the cuboid. The internal cuneiform is produced 

 distally, as is the corresponding bone of the manus. 



Order Edentata. — In the Sloths the pes much resembles 

 the manus in its general characters, being long, very narrow, 

 and curved, terminating in strong, compressed, pointed 

 ungual phalanges, supporting hook-like claws. The tarsus 

 is short ; the astragalus has a deep, cup-shaped cavity on its 

 outer side, into which a conical projection of the lower end 

 of the fibula is received. 



The appellation " Two-toed " applied to the genus Cho- 

 Icepus refers only to the anterior limb, for in the pes the 

 three middle toes are functionally developed, and of nearly 

 equal size in both the genera of the family. 



In Bradypus the tuber calcanei is long, compressed, and 

 widened at the extremity. The tarsal bones have a great 

 tendency to ankylosis. The first and fifth metatarsals are 

 very rudimentary, and support no phalanges. The proxi- 

 mal phalanges of the three middle digits are very short, and 

 coalesce very early with the metatarsals, as in the corre- 

 sponding part of the upper extremity. 



In Cholo&pas, the tuberosity of the calcaneum is very 

 small. The tarsal bones remain distinct from one another. 

 The proximal phalanges of the three middle digits are 

 extremely short, but not ankylosed with the metatarsals. 

 The first and fifth metatarsals are about three-fourths of the 

 length of the others, flattened, and gradually diminishing in 

 size to their free ends. 



In nearly all the members of the Entomophagous section 

 of the Edentata, the pes is much more normal in type, and 



