5&6 



REPTILES. 



Fig. 



Some Peculiarities in the Organs of Chelonia. 



The brain of the adult shows a slight curvature. In Chelonians and 

 in all higher animals except serpents, there are twelve cranial nerves, 

 for in addition to the usual ten, a hypoglossal to the tongue, and a 

 spinal accessory to cervical muscles are ranked as the eleventh and 

 twelfth. 



The gullet often bears internally pointed horny papilliE directed 

 downwards. There are blind pockets or anal bursce connected with 

 the cloaca. 



The heart is three chambered, but an incomplete septum divides the 

 ventricle into a right portion 

 from which the pulmonary 

 arteries and the left aortic 

 arch arise, and a left portion 

 fronr which the right aortic 

 arch issues. From the right 

 aortic arch, which contains 

 more pure blood than the 

 left, the carotid and sub- 

 clavian arteries are given off. 

 The left aortic arch gives off 

 the coeliac artery before it 

 unites with the right. 



Unlike other Reptiles, the 

 Chelonians are said to have 

 no renal portal system. 



The lungs are attached to 

 the dorsal wall of the thorax, 

 and have only a ventral in- 

 vestment of peritoneum ; 

 each is divided into a series of compartments into which branches of 

 the bronchus open. There is a slight muscular diaphragm. 



In the males, the kidney, the epididymis, and the testes, lie adjacent 

 to one another on each side. The males have a grooved penis attached 

 to the anterior wall of the cloaca. There is a urinary bladder. 



Classification of Chelonia. 



I. Athec/e. Vertebrae and ribs free from bony shield. Skull 

 without descending processes from parietals. 

 Sphargicte, leather turtles, with flexible carapace. Dernwchelys 

 coriacea, the only living species, the largest modern Chelonian, some- 

 times measuring six feet in length. It is widely, but now sparsely, dis- 

 tributed in tropical and temperate seas, and is said to be herbivorous. 

 II. Thecophora. Dorsal verteliraj and ribs fused in the carapace. 

 Parietals prolonged downwards. Incluiiing the following and 

 other families. 

 Chelonida-, marine turtles, with tin-like feet, and partially ossifieil 

 carapace. They occur in intertropical seas, and bury their soft-shelled 

 eggs on sandy shores. The green turtle (Chcloiic viyidis) is much 



heart. 



-Dissection of Chelonian 

 (After Huxley. ) 



r.7'., Right half of ventricle ; s, septum ; /.-'., 

 left half of ventricle: ra, right auricle; La., 

 left auricle ; Lew, left aortic arch ; r.ao, right 

 aortic arch ; p. a., pultnonary arch. 



