CHARACTERS OF CHELONIA 



689 



in others, long horny papillae pointing downwards ; it is probable that 

 these help to tear up the food (seaweed in the case of the turtle). 



The heart (see Fig. 404) 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, from which the 

 right aortic arch issues. From the right aortic arch, which contains 

 more pure blood than the left, the carotid and subclavian arteries are 

 given off. The left aortic arch gives off the cceliac artery before it 

 unites with the right. 



The lungs are attached to the dorsal wall of the thorax, and have 

 only a ventral investment of peritoneum ; each is divided into a series 

 of compartments into which branches of the bronchus open. There is 



Fig. 400. — Pectoral girdle of a Chelonian. 



G., Glenoid cavity ; SC, scapula ; P.C, precoracoid 

 . fused to the scapula ; C, coracoid ; E.G., epicoracoid 

 cartilage ; L., ligament. 



a slight muscular " diaphragm." The filling and emptying of the lungs 

 is helped by the protrusion and retraction of the head and legs, but 

 there are also " swallowing movements." There are no vocal chords, 

 but there is sometimes a feeble voice. 



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 Che Ionia 



I. Athec.^. Vertebra? and ribs free from carapace. Skull 

 without descending processes from parietals. 



Sphargidse, leathery-skinned turtles, with flexible carapace. Sphargis 



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