THE ALIMENTAEY CANAL IN SATJROPSIDA. 307 



usually traverses the osseous base of the skull, to join with 

 its fellow in the common aperture. 



The stapes is a columellif orm bone, the outer end of which 

 is attached to the tympanic membrane, where the latter is 

 developed ; but lies among the muscles when there is no 

 tympanic cavity. 



All Sauropsida possess a fenestra rotunda, as well as a 

 fenestra ovalis, and all have a cochlea, which is never coiled 

 spirally, and is more mdimentary in the Chelonia than in 

 other groups. Three semicircular canals, an anterior and 

 posterior vertical, and an external horizontal, are connected 

 with the membranous vestibule. In Aves, the anterior 

 vertical canal is very large in proportion to the others, and 

 the adjacent crura of the two vertical canals overlap before 

 they unite with one another. 



Labial and buccalglands are developed in some Sawopsida, 

 and one of them, on each side, attains a large development in 

 the poison glands of the venomous snakes. Well- developed 

 sublingual, submaxillary, and parotid glands appear in 

 Birds, and the sublingual glands attain an immense size in the 

 Woodpecker. The tongue varies greatly, being sometimes 

 obsolete, as in the Crocodile and some birds [e.g. the Peli- 

 cans), sometimes horny and even spinose, sometimes fleshy. 

 In the snakes, and some lizards, the tongue is forked, and 

 capable of retraction into a basal sheath. In the Cha- 

 masleons, it is clubbed at its extremity, and can be retracted 

 or protruded by the invagination or inversion of its hollow 

 stem. 



The alimentary canal of the Sauropsida is generally 

 divided into an oesophagus, a simple stomach, a smaU 

 intestine and large intestine, which last always terminates 

 in a cloaca. It is invested by a peritoneal coat, which 

 generally follows all the curvatures of the intestine. But 

 in the Ophidia, the folds of the small intestine are united 

 by fibrous tissue, and enclosed by a common sheath of 

 peritoneum. 



The stomach is usually a simple dilatation of the alimen. 



