198 CHARACTERS OF VERTEBRATE ANIMALS 



comes the wrist (carpus], made up of a number of small elements, 

 arranged in a near or proximal and a far or distal row. The 

 proximal row consists of three elements a preaxial radiate, so 

 called because it is on the radial side, an intermedium in the 

 middle, and an ulnare on the side of the ulna. The distal row of 

 carpal elements consists of five carpalia for the support of the 

 five fingers, and called, beginning on the preaxial side, carpale i, 

 carpale 2, &c. Wedged in between the two rows of carpal elements 

 is a centrale, named from its central position. The five carpalia 

 support the five fingers, each of which, has a metacarpal at its 

 base, followed by slender phalanges, two of these going to the 

 thumb or first digit, and three to each of the others. 



The free part of the hind-limb is supported by elements which 

 correspond precisely with those of the fore-limb, as in the following 

 table : 



Fore-Limb. Hind-Limb. 



1. Upper-arm bone (humerus). i. Thigh-bone (femur). 



2. Bones of fore-arm : 2. Bones of lower leg : 



(a) Preaxial radius. (a) Preaxial tibia. 



(b) Postaxial ulna. (b) Postaxial fibula. 



3. Wrist (carpus): 3. Ankle (tarsus): 



(a) Radiale, intermedium, ulnare (a) Tibiale, intermedium, fibulare. 



(b} Centrale. (b) Centrale. 



(c) Carpalia: i, 2, 3, 4, 5. (c) Tarsalia: i, 2, 3, 4, 5. 



4. Metacarpus: 4. Metatarsus: 



Metacarpalia : i, 2, 3, 4, 5. Metatarsalia : i, 2, 3, 4, 5. 



5. Phalanges: 5. Phalanges: 



Thumb, 2 ; other digits, 3 each. Great toe, 2 ; other digits, 3 each. 



If we compare the skeleton of the lizard's limbs with the theo- 

 retical arrangement just described, the result will be as follows: 



Fore-Limb Shoulder-Girdle. The dorsal scapular section is 

 represented by two parts an upper supra-scapula and a lower 

 scapula proper, while on the ventral side both coracoid and pre- 

 coracoid of the theoretical type are seen. But over and above 

 this we find additional parts in the form of a slender collar-bone 

 (clavicle) situated in front, and running towards the middle line to 

 join its fellow, besides which there is a cross-shaped inter-clavicle, 

 belonging to neither girdle, but coming between them, and also 

 attached to the sternum. Free Limb. Here there is a very close 

 correspondence with the theoretical type, differences being chiefly 

 seen in the presence of an accessory bone in the carpus coming 



