306 SYSTEMATIC ZOOLOGY 



fonidae, the jaws are toothless and the skin is generally rough 

 and warty. They are most abundant in the tropics, but are dis- 

 tributed over the whole world The largest of all is Bufo mar- 

 inns, of tropical America, whose head and body attain a length 

 of twenty centimeters. Almost as large is the Bufo borcas of 

 the Pacific slope of North America. The common toad of our 

 Middle, Northern, and Western states is Bufo americanus, whose 

 musical note is heard in the spring and summer. Related to 

 these is the Bombinator igneus of Europe and Asia, which is 

 aquatic in habit. Another European toad, Alytes obstetricans, 

 is of interest because the male places the eggs, which are laid 

 in a long, gelatinous string, on his back and winds them about 

 his hind legs; there they remain until they have developed. 

 The true tree toads belong to the family Hylidae and are most 

 numerous in tropical America ; they are provided with teeth and 

 many are brilliantly colored. The most common in the United 

 States is Hyla pickeringii, whose shrill note is very noticeable 

 in the springtime. 



The frogs, like these toads, have a well-developed tongue, and, 

 while some are toothless, the true frogs have teeth in the upper 

 jaw ; they likewise have the hind legs developed for leaping, and 

 a smooth skin. The largest is our North American bullfr 

 Rana catesbiana, whose head and body attain a length of twenty 

 centimeters. There are several smaller species of this same 

 genus in Europe and many in this country. The eggs of frogs 

 are inclosed in a transparent, gelatinous envelope and adhere 

 together in irregular masses unlike the long strings of the toad's 

 eggs ; they may be found in almost any body of quiet water near 

 the shore in the spring and early summer, and rapidly develop 

 into the larva- or tadpoles (Fig. 314). 



SUBCLASS III. GYMNOPHIONA 



The Gymnophiona (Gr. yv/xiw, naked, and o<£k. serpent) are 

 vermiform Amphibia, without appendages and tailless, with the 

 skin tolded so that the animal appears ringed much like an 

 earthworm ; minute scales are present in the integument. The 

 eyes are very rudimentary and covered by the skin, while some 

 species are blind. They are found in tropical portions of South 





