88 The Alligator and Its Allies 



The tarsus is much modified and consists of 

 four elements, in two rows ; those of the proximal 

 row are much larger than the two distal elements. 

 Articulating with both tibia and fibula, as men- 

 tioned above, and with the first metatarsal and 

 one of the distal tarsalia, is the large and irregular 

 tibiale-centrale element of Reynolds (tb, tb'). 

 In the tarsus here shown it consists of two elements. 

 Post-axial in position is the calcaneum or fibulare 

 (ca), articulating with the preceding tarsal element, 

 with the fibula, with the rudimentary fifth meta- 

 tarsal, and with the distal tarsal element said by 

 Reynolds to represent the fourth and fifth tarsa- 

 lia. The calcaneum is extended caudad into a 

 prominent knob quite like the heel of the higher 

 mammals. 



The two distal tarsal bones are small; one is 

 said by Reynolds to represent the first three tarsalia 

 (t 3 ), the other (t 4 " 5 ) the fourth and fifth. Wieders- 

 heim says one of these bones represents the first 

 three tarsalia, the other the fourth. In the tarsus 

 here shown these two elements are fused. 



The foot has five digits, though the fifth is small 

 and consists merely of a small, distally pointed 

 metatarsal bone. According to Wiedersheim this 

 fifth metatarsal is fused with the fifth tarsalia. 

 The metatarsals of the first four digits are long and 

 progressively more slender from the first to the 

 fourth; each is distinctly enlarged at the ends. 

 The first digit or hallux has two phalanges, the 



