52 GENERAL ANATOMICAL CHARACTERS 



aspect of the shaft of this bone in many forms is of considerable 

 taxonomic importance. 



Pes. — The terminal segment of the hind limb is the foot or pes. 

 Its skeleton presents in many particulars a close resemblance to that 

 of the manus, being divisible into three parts: (1) a group of 

 short, more or less rounded or square bones, constituting the 

 tarsus ; (2) a series of long bones placed side by side, forming the 

 metatarsus; and (3) the phalanges of the digits or toes. 



The bones of the tarsus of many of the lower Vertebrata closely 

 resemble both in number and arrangement those of the carpus, as 

 shown in Fig. 1 7. They have been described in their most general- 

 ised condition by Gegenbaur under the names expressed in the first 

 column of the following table. The names in the second column are 

 those by which they are generally known to English anatomists, 

 while in the third column some synonyms occasionally employed 

 are added. 



Tibialei?) ) =Agt lugl =Talus 



Intermedium J 



Fibula/re = Calcaneum = Os calcis. 



Centrale = Navicular = Scaphoideum. 



Tarsale 1 = Internal cuneiform = Entocunciforme. 



Tarsale 2 = Middle cuneiform = Mesocuneiforme. 



Tarsale 3 = External cuneiform = Ectocuneiforme. 



Tarsale 4 \ _ p i • j 



Tarsale 5 J 



The bones of the tarsus of mammals present fewer diversities of 

 number and arrangement than those of the carpus. The proximal 

 row (see Fig. 18) always consists of two bones, namely the astra- 

 galus (a), which probably represents the coalesced scaphoid and lunar 

 of the hand, and the calcaneum (c). The former is placed more to 

 the dorsal side of the foot than the latter, and almost exclusively 

 furnishes the tarsal part of the tibio-tarsal or ankle-joint. The cal- 

 caneum, placed more to the ventral or " plantar " side of the foot, is 

 elongated backwards to form a more or less prominent tuberosity, 

 the " tuber calcis," to which the tendon of the great extensor muscles 

 of the foot is attached. The navicular bone (?i) is interposed between 

 the proximal and distal row on the inner or tibial side of the foot, 

 but on the outer side the bones of the two rows come into contact. 

 The distal row, when complete, consists of four bones, which, be- 

 ginning on the inner side, are the three cuneiform bones, internal 

 (c 1 ), middle (c 2 ), and external (c 3 ), articulated to the distal surface 

 of the navicular, and the cuboid (cb), articulated with the calcaneum. 

 Of these the middle cuneiform is usually the smallest in animals 



1 Cope and Baur consider that the astragalus corresponds only with the inter- 

 medium, and that the tihiale may exist as a distinct element. 



