324 CLASS REPTILIA. 



and trigeminal nerves, and are to be regarded as a second 

 olfactory organ especially developed in connection with the 

 mouth. The tongue is always well developed. In snakes and 

 many lizards this organ serves for feeling and in other cases, e.g. 

 the chameleon, for the prehension of food. 



Alimentary canal. Teeth are usually present on the 

 premaxillae, maxillae, and dentary, and frequently on the pala- 

 tine and pterygoid. They are continually replaced, and are 

 pleurodont, acrodont, or thecodont (p. 343). They are conical 

 or hooked, and are adapted for prehension not for mastication 

 (except in some extinct forms). In Chelonia teeth are absent, 

 being replaced by the horny epidermal beak-like covering of 

 the jaws. 



True salivary glands are usually absent. There is a sublingual 

 in Chelonia. Labial glands, both upper and lower, and palatal 

 and lingual glands are frequently present. The poison glands 

 of snakes are upper labial. 



The alimentary canal presents no remarkable features. The 

 large intestine is short and often has a small caecum. It leads 

 into the cloaca which receives the urinogenital ducts and in 

 Lacertilia and Chelonia an allantoic bladder. Tlie anus is a 

 transverse slit in lizards and snakes, a longitudinal slit or a 

 roundish opening in chelonians and crocodiles. 



The Reptilia breathe exclusively by lungs, which have the 

 form of spacious sacs with alveoli in the walls (snakes, lizards), 

 or the cavity is much broken up and the lungs are spongj' 

 {Chelonia, Crocodilia). The trachea is long and dififerentiated 

 in front into a larynx which opens into the pharynx by a slit- 

 like glottis. An epiglottis is foimd in many tortoises, snakes 

 and lizards. Vocal chords are present only in chameleons, 

 geckos and crocodiles. 



In lizards and crocodiles peculiar adhesions may be formed 

 between the lungs and the liver. In crocodiles * these are exten- 

 sive and complicated and constitute a diaphragmatic mem- 

 brane separating the pleural cavities from the general body- 

 cavity. 

 Vascular system.f In all reptiles the heart consists of a 



* Butler, P.Z.S. 1889, p. 452. 



t Sabatier, Le Coeur, Montpellier, 1873. Rose, Morph. Jahrb., 16, 1890, 

 p. 27. G. Fritsch. Arch. f. Anat. and Phyaiologie, 1869, p. 654. 



