174 



ANATOMY OF VERTEBRATES. 



108 



I II III IV V 



Laud Tortoise. CLI. 



The distal end is transversely extended and divided anteriorly 



into two condyles. The shaft has a medullary 

 cavity smaller than in land lizards. The radius, 

 fig. 57) t, fig. 109, Z>, 54, has an oval head, an 

 almost cylindrical and straight shaft, with an 

 oblong and subcompressed distal end. The ulna, 

 fig. 57, s, fig. 109, #, 55, articulates with the 

 outer condyle of the humerus by an oval facet, 

 the thick convex border of which swells out be- 

 hind like the beginning of an ' olecranon ; ' the 



O O 



shaft of the ulna is compressed transversely and 

 curves slightly outward ; the distal end is less 

 than the proximal one, and articulates with the 

 second and third bones of the carpus. The first 

 metacarpal supports two phalanges, I, the second three, n, the 

 third and fourth, each four, the fifth, V, three phalanges which 

 109 are very slender ; but the proportions are shown 



in the cut ; only the toes, I, n, and in, have the 

 claw. All are basally united by a short web, 

 but the fore-foot is chiefly used in movements 

 upon land. 



In the Monitor ( Varanus niloticus) the supra- 

 scapula is a broad semiossified plate : the 

 scapula is short and broad, and appears to 

 have coalesced with the coracoid. This bone 

 is much expanded, and has two deep notches 

 anteriorly, and a perforation near the humeral 

 articulation. In some Lizards it sends for- 

 ward an acromial process. The coracoid is 

 shorter and broader than in the Crocodile, 

 abuts against the upper margin of the rhorn- 

 boidal sternum, and sends off two processes 

 from its anterior border, the one next the sca- 

 pula abutting against the transverse branch of 

 the episternum ; the other against the sub- 

 ossified epicoracoid : this element overlaps that 

 of the opposite side. In the Monitor, as in 

 most Lizards, there are distinct clavicles : usu- 

 ally long and slender bones, with more or less 

 expanded extremities, extending from the body 

 of the episternum and accompanying the trans- 

 verse branch to abut against the scapula ; and sometimes also 

 reaching the outer process of the coracoid. In Lacerta, Cuv. 



Bonos of fore-arm and 

 foot, Crocodile. CLI. 



