ORDER CHELONIA, 7 



genus, this frame-work always remains cartilaginous. 

 The vertebrae of the neck and tail alone are move- 

 able. 



These two osseous envelopes being covered imme- 

 diately by the skin or scales, the omoplate, and 

 all the muscles of the arm, and of the neck, instead 

 of being attached to the ribs and the spine, as 

 in other animals, are attached underneath. It 

 is the same with the bones of the pelvis, and all the 

 muscles of the thigh, which might lead us to term 

 the tortoise, in this point of view, an inverted 

 animal. 



The vertebral extremity of the omoplate is arti- 

 culated with the carapace ; and the opposite extre- 

 mity, which may be considered as analogous to the 

 clavicle, is articulated to the plastron, so that the 

 two shoulders form a ring, into which the oesophagus 

 and the trachea pass. 



A third osseous branch, greater than the other 

 two, is directed downwards, and hindwards, and 

 represents, as in the birds, the coracoid process ; 

 but its posterior extremity remains free. 



The lungs are very much expanded, and in the 

 same cavity as the other viscera.* The thorax 

 being immoveable in the greater number of species, 

 it is by the play of the mouth that the tortoise 

 respires, holding the jaws well closed, and lowering 



* Remark, that in all the reptiles, in which the lungs penetrate into the 

 abdomen (and the crocodile is the only one in which this does not take 

 place), they are enveloped, as well as the intestines, in a fold of the 

 peritoneum, which separates them from the abdominal cavity. 



