150 THE VERTEBRATE SKELETON. 



The tarsus consists of eight small bones arranged in a 

 proximal row of three, the tibiale, intermedium and fibu- 

 lare, and a distal row of four tarsalia, with one bone, the 

 centrale (fig. 23, A, 7), interposed between the two rows. 

 In the specimen examined, the tibiale, is a small bone 

 articulating with the tibia, the intermedium (fig. 23, A, 5) 

 is larger and articulates with both tibia and fibula, the 

 fibulare is the largest of the three and articulates with the 

 fibula. 



The bones of the distal row are tarsalia 1, 2, 3, and a 

 bone representing 4 and 5 fused. In the specimen examined 

 tarsale 1 is pushed away dorsal ly (fig. 23, A, 8), so as to lie 

 between the tibiale and tarsale 2. All the tarsal bones are 

 small and somewhat polygonal, and are connected with one 

 another, and with the tibia and fibula on the one hand, and 

 with the metatarsals on the other by a thin layer of cartilage. 



The five digits of the foot each consist of a metatarsal 

 and of a certain number of phalanges. In the specimen 

 examined, owing to the shifting of tarsale 1, the first meta- 

 tarsal as well as the second articulates with tarsale 2, while 

 the fifth metatarsal articulates partially with the bone repre- 

 senting the fused tarsalia 4 and 5, partially with the fibulare. 

 All the bones of the digits except the distal phalanges are 

 terminated at each end by cartilaginous epiphyses, the distal 

 phalanx of each digit has a cartilaginous epiphysis only on its 

 proximal end. 



The first, second, and fifth digits have two phalanges 

 apiece, the third and fourth have three. 



Figure 31 B, showing a Newt's tarsus copied from Gegen- 

 baur, has precisely the arrangement generally regarded as 

 primitive for the higher vertebrates, except that tarsalia 4 

 and 5 are fused. 



