316 SYSTEMATIC ZOOLOGY 





ments, so that the mouth is very distensible, and they can con- 

 sequently swallow relatively large animals, although their powers 

 in this direction have been greatly exaggerated in popular nar- 

 rative. The tongue is slender, bifid, and protrusible, and when 

 retracted lies in a sheath on the floor of the mouth ; owing to 

 little grooves in the jaws, the tongue can be thrust out even 

 when the mouth is closed. The teeth are sharp and recurved 

 so that they serve for holding the prey while it is being swal- 

 lowed ; they are not permanent, but may be renewed when 

 necessary ; in the poisonous serpents the poison fangs are 

 either grooved or tubular, thus affording a channel for the 

 poison. All serpents feed on living animals, which they swal- 

 low whole and then slowly digest ; during this time they are 

 very sluggish and inactive. Some also feed upon eggs. 



As might be expected from the greatly elongated body, the 

 number of vertebrae is very great; there may be over four hun- 

 dred, and the ribs are also numerous, there being a pair to each 

 abdominal scute. The motion of the body is produced by the 

 lateral bending of the vertebral column and the movement of 

 the ribs ; the scutes press against any roughness on the surface 

 over which the animal is moving and thus produce the locomo- 

 tion of the body ; a serpent cannot move forward upon a per- 

 fectly smooth surface. Most of the Ophidia are oviparous, but 

 some bring forth their young alive. Many are brilliantly 

 colored ; and often thev have a protective coloration, — that is to 

 say, they closely resemble the colors of the objects amongsl 

 which they habitually live. They are mostly tropical, although 

 many occur in temperate regions. In their habits the} - vary 

 considerably ; some live underground, buried in the earth or 

 sand; some live among rocks or in deserts; some are arboreal 

 and others aquatic, remaining a part or all of the time in the 

 water, either salt or fresh. Thev cast the outer, horny layer of 

 their skin periodically, and during some season of the year 

 remain quiescent, taking no food ; in the tropical countries this 

 is the hottest season, and in the temperate regions the winter. 

 Serpents are capable of domestication to some extent, and even 

 poisonous species can often be handled with impunity by tlv s 

 accustomed to them. In many species instances have been 

 observed (^' snakes taking an interest in their mates; when one 



