REPTILIA. 83 



number of ribs, employed in respiration ; no sternum nor 

 movable eyelids, nor tympanum ; tongue very extensible, 

 terminated by two long movable points of a consistence nearly 

 like horns, and contained, while at rest, in a membranous 

 case ; the mouth furnished with teeth fit only to retain the 

 prey ; heart with two auricles, and only one ventricle ; only 

 one lung, extending far towards the posterior portion of the 

 body; voice, when any, consisting in a dull hiss; eggs agglu- 

 tinated in the form of a chaplet, and quite soft, although en- 

 veloped in a calcareous substance. Three families. 



FAMILY I. ANGUINA. 



Three eyelids ; imbricated scales over all the body ; most 

 usually the rudiment of. a shoulder or pelvis under the skin. 



FAMILY II. SERPENTIA. 



No sternum nor vestige of shoulder ; no third eyelid nor 

 tympanum. In this family are comprised the greater part 

 and the most singular of the Ophidia. Two tribes. 



TRIBE I. AMPHISBCENA. 



Mouth not dilatable ; head uniform with the body, permit- 

 ting them to walk equally well backwards or forwards ; body 

 covered with scales. 



TRIBE II. SERPENS PROPER. 



Jaw so arranged as to permit a wide opening of the mouth ; 

 the two branches are not soldered, and can separate laterally; 

 the tympanal bone to which they are attached is itself sus- 

 pended to another bone articulated to the cranium ; the two 

 upper maxillary bones preserve also their mobility ; besides 

 the teeth of the jaws there is a double range in the palatine 

 arches. Two sections. 



Section I. Non- Venomous. 



No movable teeth either with channel or tube ; all are 

 fixed strongly ; in the roof of the mouth four rows nearly 

 equal, two below. Two genera. 



