440 



ANATOMY OF VERTEBRATES. 



299 



tion than truly salivary, as exercising any alterant influence on 

 the nature of the food. 



A ' velum palati ' is developed only in the CrococUlia : an 

 epiglottis is not present in any Reptile : the basihyal valve of the 

 Crocodiles is analogous to one, and some lizards show a rudiment of 

 epiglottis. The sides of the pharynx are cleft by the gill-slits in the 

 perennibranchiate Batracltia ; and one slit on eacli side remains 

 open in some of the caducibranchiate species, as, e. g., in Menopoma. 

 In the Siren there are three clefts on each side, defended by inter- 

 locking pointed processes, closely resembling the narrower of the 

 five lateral branchial clefts in the Lepidosiren, fig. 316, l, 3, 4, 5. 

 The oesophagus is short and wide in Batrachia, fig. 294, d, c, 



long and wide in Oplndia, fig. 300, d, 

 e, f, of moderate length and width in 

 Chelonia, narrower in Crocodilia, fig. 

 298, e, and still more so in insecti- 

 vorous Lacertilia, fig. 303, e. It is 

 remarkably dilatable and thin-coated 

 in Snakes, as at fig. 300, f, in which 

 its intrinsic propelling power is sup- 

 plemented by the constriction of the 

 surrounding trunk-muscles during 

 the deglutition of bulky prey. The 

 other chief peculiarities in the struc- 

 ture of this part of the alimentary 

 canal of Reptiles are, the perforation 

 of its walls by certain elongated and 

 enameled hypapophyses in Deirodon, 1 ante, p. 393, and the produc- 

 tion of the lining membrane into pointed processes, directed to the 

 stomach, and covered by thick epithelium in the Turtles ( Chelone).* 

 These aid in the deglutition of the long slippery seaweeds on 

 which the Turtle feeds ; in carnivorous Chelonia they are not 

 present ; the lining membrane in Testudo rndica, e. g., is thrown 

 into longitudinal ruga? when undistended, and presents a fine 

 reticular and porous surface. The ciliated epithelium is con- 

 tinued along the gullet in Triton, fig. 294, d, and in the larva? of 

 Toads and Frogs. 3 The muscular tunic of the gullet is strongest 

 in the Turtles. 



The stomach presents, in Reptiles, its most simple form in the 

 Ophidian and Batrachian orders, especially in the ichthyo- and 



Retroverted processes iu cesopliagus of 

 Turtle (Chelone). COL. 



Jourdan, in ccxlii. torn. vi. p. 160. 



xx. torn. i. p. 126, preps, nos. 460, 461; XLIII. pt. iv. pi. v. fig 7. 



CCXL1II. torn. i. p. 191. 



