REPTILES. 



unbending the arches into which the body is successively 

 thrown. The body can advance or retreat by either extre- 

 mity, with nearly equal readiness. The eyes are so small, 

 that, with many, they have passed unobserved. 



a. Serpents with a third eye-lid. 



In the animals of this group, the teeth are "small, and 

 nearly of equal size. The tongue is notched in a crescent 

 form. The ribs are more or less united, to supply the 

 place of a sternum. When irritated, the body is thrown 

 by the muscles into a very rigid state, in which condition it 

 breaks into fragments by the slightest stroke. None of the 

 species are considered venomous. The condition of the ru- 

 diments of some of those organs possessed by the Saurian 

 reptiles, which may here be detected, justify the subdivi- 

 sion of the three genera here contemplated. 



(1.) Traces of scapular and clavicular bones occur under 

 the skin. There is likewise a minute sternum and an im- 

 perfect pelvis. Though the rudiments of the extremities 

 can be detected within the skin, there are no vestiges of legs 

 or feet on the outside. 



35. OPHISAURUS. The tympanum is externally visible. 

 The maxillary teeth are conical ; and, besides these, there 

 are two groups on the palate. O. ventralis. 



36. ANGUIS. Snake. The tympanum is concealed. No 

 palatine teeth. The maxillary teeth are compressed and 

 recurved. A. fragilis. 



(2.) No vestiges internally of pelvis, scapula, clavicle, 

 or sternum. The anterior ribs, however, are united by 

 intervening cartilaginous productions, which serve instead 

 of a sternum. 



37. ACONTIAS. The teeth are conical. There is the 

 rudiment of a second lobe of the lungs. A. meleagris. 



VOL. n. T 



