556 TEXTBOOK OF ZOOLOGY 



Both of our species lead a subterranean existence, boring tuimels 

 in which they move backward and forward with equal ease. 



Suborder Ophidia (Serpentes) (Snakes). — No group of reptiles is 

 of greater natural interest to man than the snakes. Superstitions 

 and stories relating to snakes are as old as written language. Many- 

 religions and cults have used the serpent as a symbol of good or 

 of evil. In many regions of the world today many of the most 

 poisonous of snakes are venerated and protected by the natives. 

 The snake dance of the Hopi Indians of our own country is a well- 

 known example of the symbolic use of snakes. 



The ophidians are highly modified vertebrates. Their anatomical 

 structure indicates that they have been derived rather recently, 

 geologically speaking, from lizardlike ancestors. Some lizards are 

 totally limbless, while some snakes of the family Boidae have vestiges 

 of the posterior pair of limbs. In the structure of the jaws there 

 is close similarity between some snakes and some lizards. 



Upon the basis of structure and arrangement of teeth snakes 

 have been arranged into the following four groups: 



The Aglypha, or those with solid, ungrooved teeth. Our harmless 

 snakes all have this type of dentition. 



The Opisthoglypha, or those having the posterior maxillary teeth 

 grooved. These snakes are venomous but seldom dangerous to man. 

 The position of the venom conducting teeth makes it difficult for 

 the snake to inflict a wound on man. The lyre snakes (Trimorpho- 

 don) of the Southwest, the black-headed snakes (Tantilla) of the 

 Southern States, and a few other rare snakes belong to this group. 



The Proteroglypha are those that have the anterior maxillary 

 teeth grooved and often enlarged and elongated. Many of the most 

 dangerous snakes in the world belong to this group. The coral 

 snakes, cobras, and sea serpents have this type of dentition. 



The Solenoglypha, or those having hollow, hinged fangs in the 

 anterior part of the mouth. The rattlesnakes, copperheads, water 

 moccasins and their relatives make up this group. They are all 

 venomous and dangerous to man. 



There are approximately 2,300 known species of snakes. Of this 

 number, some 225 species are venomous; but 75 of these poisonous 

 species are so small or rare that there are only 150 to 175 species 

 that man need fear. 



