Chap. II. THE CINOSTERNOID.E. 349 



too, in tlcsconding to the plastron, rcaolie.s far forward ; it is short across tlie pubis 

 and ischium, and the processes of the pubis extend sidewise rather than forward ; 

 the ihac bones arch outward, but are about the same width apart at the shoul- 

 der joints as at the sacriuu. The shoulder apparatus and pelvis approaching each 

 other so nearly at the plastron, and filling the intervening space with their mus- 

 cles, press the organs of digestion and respiration, and the other viscera, up into 

 the carapace. The bones of the shoulder apparatus and of the pelvis, and those of 

 the legs and feet, are all slender. The feet are short and round. The toes are 

 freely movable, and joined by a web, and the whole foot very flexible within 

 itself, and at the joint with the forearm and leg. 



The head is long from the orbits of the eye backward, and short from thence 

 forward ; it is pointed in front. The upper maxillaries and intermaxillaries retreat 

 backward and inward, so as to make the mouth small, and carry it far inward, 

 under the head. The outer surfiice of the lower jaw also reti'eats in the same 

 manner, so that the sides of the front part of the head slant inward from the top 

 to the bottom. This makes the lower jaw short, and enables the temporal mus- 

 cles to act upon it to advantage. These muscles have a long attachment to it, and 

 are themselves very large, so that the bite of the animal is strong. The alveolar 

 surfaces are broad, and the edges sharp ; the lower jaw always terminates in a 

 sharp point. The trough by the side of the brain-box, over which the temporal 

 muscles pass, is very long ; but the mastoids project but little backward, beyond it 

 The arch from the top of the skull, back of the eye, is very short ; thus difl'ering 

 essentially from the broad roof of the Chelydroidte. The temporal arch, from the 

 ear opening forward, over the temporal muscle, is wide. The maxillaries reach 

 back under the jugals to the temporals. The bottom of the skull-box and the 

 palate rise continually forward to the nasal region, and approach so nearlv to 

 the top of the skull as to leave only just room enough for the passage of the 

 olfactory nerve. The neck is long, but has not nearly as large a muscular 

 apparatus as in the Chelydroidic ; it is also much more slender. 



The shield is everywhere covered on the outside with large horny epidermal 

 scales, which, in difl'erent genera, present considerable diflerences in their arrange- 

 ments, especially upon the plastron. The free skin is loose, and folded around 

 the body and limlis; its epidermis is thickened into scales in several isolated 

 places on the legs, and under the feet, and there only these scales are contin- 

 uous and imbricated. The average size of the representatives of this family is 

 smaller than in any other family of Testudinata. The largest, which is about 

 nine inches long, is not nearly as large as the smallest t)f the Chelvdroida-, or 

 as the largest of either of the other families ; and the smallest Ozotheca, which is 

 about four inches long, is not larger than the smallest of the Emydoida). 



