84 ORGANS OF SUPPORT, 



bone. In the marine turtles, and in the fresh -water emydes, 

 as seen in the skull of the emys expansa (Fig. 44. h, h,) 

 the parietal bones rise upwards on the median line of the 

 head, and extend laterally over the temporal fossa. The 

 tympanic bones are large, fixed by suture as in the croco- 

 diles, and extend downwards to form a condyle for the 

 articular cavity of the lower jaw. The two posterior (g, g,) 

 and the two middle 



frontals bound the orbits 

 above, and the two malar 

 bones (i, i,) behind. The 

 two anterior frontals (a, 

 a,) bound the orbits in 

 front, and expand over 

 the nasal aperture, like 

 nasal bones. The inter- 

 maxillaries are narrow, 

 vertical, with an extensive palatine surface, and like the 

 superior maxillaries, they present a sharp alveolar edge, 

 which is covered with the cutting, horny, superior mandible. 

 Behind the two jugal bones (i, i,) are the expanded squamous 

 portions (k, k,) of the temporals, and behind these the two 

 long, descending, mastoid bones (m, m.) Anterior to the 

 mastoid bones (m* m,) are the upper portions of the tym- 

 panic bones (r, r.) Two portions (o, o,) detached from the 

 condyloid elements (q, q,) of the occipitals, are termed ex- 

 terior occipitals by Cuvier. The ossicula auditus are an- 

 chylosed together, as in many of the lower vertebrata. The 

 symphysis of the lower jaw is anchylosed at a very early 

 period of growth, as in birds. From the importance of the 

 os hyoides in the motions of respiration in these animals, 

 where the ribs are fixed,, its body and cornua are very large 

 and strong. 



The arms of the tortoise are fixed in a state of pronation, 

 to' strengthen them for the support of the heavy trunk ; 

 and, like those of the legs, all their bones are short and 

 massive in their proportions. The humerus is much bent, 

 the radius and ulna short, strong, and with a very broad 

 articular surface at the carpus, and the succeeding bones of 

 the hands are short and almost cubical, for support and for 

 digging, like those of the mole. The same proportions are 



