48 CLASS REPTILIA. 



sometimes terminated by a sharp and corneous point, which 

 has been considered as a defensive weapon. Under this tail 

 is the anus, which also constitutes the aperture for the organs 

 of generation, both in male and female. 



Having enlarged on the osteology of the tortoise in another 

 place, we shall content ourselves here by briefly stating that 

 their frontal bones constitute only the vault of the orbits ; 

 that the parietals are three times as long as those ; that the 

 mammillary processes are considerable ; that the very nume- 

 rous bones of the face cover each other by their edges, which 

 are basiled ; that there are seven or eight vertebrae in the 

 neck, two of which alone have spinous processes ; that there 

 are from eight to eleven in the back, and three to the sa- 

 crum, which, as has been observed in the text, are soldered 

 to the carapace ; and that the vertebrae of the tail vary in 

 number according to the species, and their condyle is turned 

 in a contrary direction to that of the neck. 



When the plastron or breast-plate of a tortoise is removed, 

 we find a membranous periosteum-like parchment, which is 

 nothing in fact but the skin of the belly. When this is open 

 we can see the different muscles which give play to the head 

 and feet, and the peritoneum is then visible. This, again, 

 being open, we see the intestinal canal, the liver, and the 

 lungs, which consist of two lobes separated by the dorsal spine. 



To Townson we owe the discovery of the very remarkable 

 manner in which tortoises respire, a mode to which there is 

 nothing analogous in other animals, because no other has, like 

 them, an immoveable thorax. 



This anatomist, on examining some muscles of the region of 

 the flanks, placed on the sides of the hind legs, and at the 

 extremity of the lobes of the lungs, was convinced that two 

 of them were distinct, though strongly joined in the middle. 

 The first originates at the carapace, near the dorsal spine. 



