CLASSIFICATION OF AMPHIBIA 229 



phibians of the tropical regions. They have from two hundred 

 to three hundred vertebrae. There are no gills or gill-slits in the 

 adult stage. Their mode of locomotion is much like that of the 

 earthworm. It is produced by the peristaltic motion of the 

 skin, aided by the numerous ring-shaped constrictions. The 

 eyes are vestigial and concealed beneath the skin. 



The only family is Ccecili'idae, with some forty species. Some genera, 

 as Ichthyophis, have small scales embedded in the skin. Others, as the 

 Typhlonectes of Guiana and Venezuela, are scaleless. T. compressicauda 

 is 18 inches long and J inch in diameter. Its color is from an olive brown to 

 black, which is the general color of most species. Some, as Ichthyophis, are 

 oviparous; others, as Dermophis, are viviparous. 



Order III. Urode'la or Cauda'ta. — These are the tailed and 

 limbed amphibians. They have four limbs, as in the toads and 



Fig. 187. — Siren {Si'ren lacerti'na). (Chapin and Rettger, Englehard & 

 Co., Publishers.) 



frogs; or two, as in the Siren. The skin is smooth and slimy. 

 Locomotion is accomplished mostly by body motion, aided by 

 the weak limbs, in strong contrast with the limb-motion of the 

 frogs and toads. They are not very common as compared with 

 frogs and toads. Newts and salamanders are examples. 



. Siren'idoB is a small family of two genera of one species each. The 

 "mud-eel" (Siren lacertina) (Fig. 187) of the southern United States is 2 or 

 3 feet long. Posterior limbs are wanting, and the weak anterior limbs have 

 four digits. The tail is long, compressed, and thin. There are three pairs 

 of gills, but they atrophy in the young and are redeveloped subsequently .^ 

 The mud-eel is a harmless creature, burrowing in the mud of ponds and 

 ditches. Dorsally it is dark colored, but lighter ventrally. Sometimes 



1 Gadow, p. 136. 



