526 THE VERTEBRATE SKELETON. 



astragalus is very flat, and the tarsals interlock to a slight 

 extent, the cuboid articulating with both calcaneum and 

 astragalus. 



The pes in the PROBOSCIDEA much resembles that in the 

 Amblypoda, but differs in that the astragalus does not arti- 

 culate with the cuboid, the tarsals not interlocking at all. 



In the RODENTIA the structure of the foot is very variable. 

 In Beavers the foot is very large, all five digits being well 

 developed ; the fifth metatarsal articulates with the outer side 

 of the fourth metatarsal, and not with the cuboid, and there 

 is a large sesamoid bone on the tibial side of the tarsus. In 

 the Rats, Porcupines and Squirrels, there are five digits, in the 

 Hares only four, and in the Capybara and some of its allies 

 only three. In the Jerboa (Dij)us) a curious condition of the 

 pes is met with, as it consists of three very long metatarsals 

 fused together and bearing three short toes, each formed of 

 three phalanges. Lophiomys differs from all other Rodents 

 in having the hallux opposable. 



CARNIVORA. In the Carnivora vera the pes is regular and 

 shows little deviation from the normal condition. All the 

 usual tarsal bones are present, but sometimes as in the Dogs, 

 Cats, and Hyaenas, the hallux is vestigial. Sometimes as in 

 the Bears the pes is plantigrade, sometimes as in the Cats and 

 Dogs it is digitigrade. In this respect and in the character 

 of the ungual phalanges, the pes closely corresponds with 

 the manus. In the Sea Otter (Latax) the foot is large and 

 flattened and approaches in character that of the Pinni- 

 pedia. 



In the Pinnipedia the pes differs much from that in the 

 Carnivora vera. In the Seals in which the foot cannot be 

 used for walking, and is habitually directed backwards, the 

 first and fifth digits are much longer and stouter than any 

 of the others. In the Sea Lions which can use the pes for 

 walking, the digits are all of nearly the same length, and 

 in the Walrus the fifth is somewhat the longest. 



