LIMBS OF THE TORTOISE AND TURTLE. 133 



cipitals are more produced backwards, and the entire skull 

 is more depressed than in the turtles. 



The ordinary position of the scapular extremity is a 

 state of extreme pronation, as shown in Fig. 20, with the 

 olecranon, or top of Stt, thrown forwards and outwards, 

 and the radial side of the hand, or thumb, ^, directed to 

 the ground. The humerus, 53, is strongly bent in a sig- 

 moid form, with the anconal surface convex and directed 

 upwards and outwards: the two tuberosities at the proxi- 

 mal end are much developed and bent towards the palmar 

 aspect, bounding a deep and wide groove: that which 

 answers to the external tuberosity is the smallest, and by 

 the rotation of the humerus it becomes the most internal 

 in position. The proximal row of the carpus consists of 

 four bones — viz : a large scaphoides, a small lunare, 

 wedged into the interspace of the radius and ulna, a large 

 cuneiforme, and a small pisiforme. The second row con- 

 sists of five distinct bones, corresponding with the five 

 digits ; those supporting the fourth and fifth answering to 

 the OS unciforme, the remaining three to the trapezium, 

 trapezoides, and magnum. The first and fifth of the digits 

 have each one metacarpal and two phalanges ; the rest, 

 ^V, w\ ^^;, have each a metacarpal and three phalanges. A 

 sesamoid bone is placed beneath the metacarpo-phalangeal 

 joint of the three middle digits. 



In the pelvic extremity, the femur, 65, is sigmoidally 

 bent, but in a less degree than the humerus, and is a 

 shorter bone. The patella is ligamentous : the synovial 

 joint between it and the femur is distinct from the proper 

 capsule of the knee-joint ; the fibula, QQ^ is longer and more 

 slender than the tibia, %%] a small "fabella" is articulated 

 to its upper end. The proximal row of the tarsus consists 

 of two bones, astragalus and calcaneum, which sometimes 

 12 



