6i6 REPTILIA. 



Some Peculiarities in the Organs of Chelonia 



In Chelonians and in all higher animals except serpents, there are 

 twelve cranial nerves, for, in addition to the usual ten, a spinal 

 accessory to cervical muscles, and a hypoglossal to the tongue, are 

 ranked as the eleventh and twelfth. 



The gullet of the turtle shows in great development what is hinted at 

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

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



FIG. 333. Internal view of the plastron of the 



Greek tortoise. 



* 



P., Epiplastron (clavicle?); ENT., entoplastron (inter- 

 clavicle?); HYO., hyoplastron ; HYPO., hypo- 

 plastron ; X1PHI. , xiphiplastron. 



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, 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 



