AMPHIBIA. 



227 



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Fio. 111. — o, Slphonops aTvmdatus^ one of tho Caecilmns, much reduced ; & Head of the 

 same; c Mouth, Bhowiug the tongue, teeth, and internal openings of the nostrils; d 

 Tail of the same. (After Bumeiil and Bibron.) 



Oedee ir. Ueodela or Ichthyomoepha (Gr. ichthus, a 

 fish, and morphe, shape). — In this order are a number of fish- 

 like Amphibians, of which the Newts and Land-salamanders 

 are the most familiar examples. In all the members of this 

 section, the skin is naked, and never develops any hard struct- 

 ures, and in all there is a well-developed, fish-like tail, which 

 is retained throughout life. The vertebrae are sometimes hol- 

 low at both ends {amphicoelous), sometimes hoUow behind 

 and convex or rounded in front [opisthoccdous). The ribs are 

 rudimentary and the bones of the forearm {radius and ulna), 

 and of the shank {tibia sxid fibula), are separate, and are not 

 combined so as to form single bones. 



The Ichthyomorpha are not unfrequently spoken of as the 

 "Tailed" Amphibians {Urodela), and they fall into two natu- 

 ral sections, according as the gills are permanently retained 

 throughout life, or are cast off before maturity is attained. 

 The animals belonging to the first section are often called 

 " perennibranchiate," while those belonging to the second are 

 said to be " caducibranchiate." 



Among the Perennibranchiate forms, in which the gills are 

 permanently retained after the lungs make their appearance, 

 the best-known examples are Axolotl (Fig. 113), the curious 

 JProteus anguinus, and the Mud-eel {Siren). The Axolotls 



