434 



ANATOMY OF VERTEBRATES. 



294 



of the penis ' and clitoris : in the Crocodilia, besides com- 

 municating with that structure, the peritoneal canals open out- 

 wardly upon papilla;, situated on each side of the base of the 

 penis 2 and clitoris. These are the exceptions, in the reptilian 

 class, to the typical character of the peritoneum as a closed 

 c serous ' sac. In most Reptiles pigmental cells are blended with 

 or supersede the ordinary tessellated lining of epithelial cells in 

 certain parts of the peritoneal surface. 



The mouth in Reptiles gives passage to respiratory currents 

 as well as to the food in the Perennibranchiates, and in all 

 the air-breathers along that extent of the cavity which is poste- 

 rior to the palato-nares, fig. 294, B, h : the Crocodilia alone 

 having the nasal distinct from the oral passage. 



In Chelonia, the jaws 

 with their horny covering 

 form, as in Gymnodont 

 fishes, the first portal to 

 the alimentary canal: in 

 many Batrachia the in- 

 tegument passes evenly 

 over the alveolar margins 

 of the jaws, as in fig. 294, 

 a, a : in Ophidia, Sauria, 

 and Crocodilia, a narrow 

 tract of soft and vascular 

 integument intervenes be- 

 tween the scale-clad border 

 of the mouth and the jaws ; 

 sinking; into a more or less 

 shallow groove, which de- 

 fines the lips and receives the secretion of a row of mucous 

 crypts : but such lips are hard and inflexible : in certain Frogs and 

 Toads they are of softer texture : but in none are produced or 

 prehensile. 



The walls of the mouth expand into pouches in certain 

 Reptiles, as e. g. at the sides of the face in male Frogs, below the 

 tongue in Hyla, and produced from the same part into a conspicu- 

 ous oular bas;, as in the Draco volans, fig. 303, d. But these 

 pouches receive air, not, as in some higher Vertebrates, food ; and 

 usually relate to the powers of voice. 



The bony walls of the mouth have been already described ; the 



1 xx. vol. iv. p. 62, preps, nos. 2448 — 2451. 



2 lb. vol. iv. p. 00, prep. no. 2439 ; and ccxxxvn. p. 153. 



Ciliated surface of the mouth and gullet, Triton. 



CCXXXVIII. 



