34 THE HIND FOOT OR PS. [CHAP. 



INSECTIVORA the tarsus is quite normal, and there are five 

 digits, all with curved, pointed, moderately developed 

 ungual phalanges, the hallux being the shortest. In the 

 Mole, the pes is narrow, having none of the modifications 

 of structure observed in the manus, except that there is 

 an unusually large slender sesamoid on the tibial side of 

 the tarsus, corresponding to the falciform bone of the fore 

 limb. In the Water Moles (Myogale), the pes is remark- 

 ably large and almost fin-like. 



In the African genera Petrodromus and Rhynchocyon, the 

 hallux is only represented by a rudimentary metatarsal. 

 The last-named animal has a remarkably elongated pes, 

 produced partly by the length of the metatarsals, and partly 

 by a peculiar elongation of all the bones of the distal 

 row of the tarsus, the cuboid and three cuneiform bones. 

 Contrary to what occurs in the Galagos, the navicular and 

 calcaneum are of normal proportions. 



Order CHIROPTERA. The tarsus is very short ; the tuber 

 calcanei is a slender curved process sometimes of con- 

 siderable length, supporting the interfemoral membrane ; 

 the metatarsals are equal and rather short ; the phalanges 

 elongated and subequal in length, the hallux being rather 

 the shortest ; the ungual phalanges are long, curved, com- 

 pressed and pointed. In the Leaf-nosed Bats (PhyllorhinincR) 

 and the anomalous genera, Thyroptera and Myxopoda all 

 the toes have only two phalanges. 



Order RoDENTiA.--The structure of the pes varies much 

 in different members of this order. In the Beaver, as in 

 most swimming quadrupeds, it is disproportionately large 

 and flat. The five digits are well developed, but the third 

 and fourth are considerably longer and stouter than the 

 others. The base of the fifth metatarsal is articulated to 

 the outer side of the fourth metatarsal, and not directly to 



