Classification 



are sensitive to the most delicate vibrations of the water pro- 

 ducing sound. The sense organs of the skin, the lateral line and 

 the ears, then, are closely related in origin and in function. 



IV. The Families of the Salientia or Tailless Ealrachia 



The Tailless Batrachia of North America, as far as known, 

 are represented by seven families, containing together twelve gen- 

 era and fifty-six species. In addition, there are a few forms that 

 rank as subspecies. All show slight modifications of one narrow 

 plan of structure, and are sometimes distinguished from one an- 

 other by close discrimination only. Their natural classification 

 rests on minute details of internal structure. It is based, for the 

 most part, first, on the ventral structure of the shoulder-girdle 

 (Fig. 5); and second, on the shapes of the sacral diapophyses, 

 those bones that form wing-like extensions of the sacral or ninth 

 Vertebra and connect directly with the ilia or hip-bones. (Fig. 6.) 



Order SALIENTIA. 



I. Superfamily Arcifera. 



The two halves of the shoulder-girdle (coracoids and 

 precoracoids) overlap in front so that the chest is capable 

 of expansion. (Fig. 5.) 



A. Sacral diapophyses dilated. (Fig. 6.) 



1 . Terminal phalanges of skeleton not claw-shaped. 



a. Vertebra opisthocoelous, ribs present, teeth on 



upper jaw. 

 Family i. Discoglossida (Ascaphus, p. 51). 



b. Vertebrae opisthocoelous, or proccelous, ribs absent, 



teeth on upper jaw. 

 Family 2. Pelobatidce (Scaphiopus, etc., pp. 43 and 53). 



c. Vertebrae proccelous, ribs absent, teeth absent. 



Family 3 Bufonidce (Toads), pp. 44 and 63. 



2. Terminal phalanges of skeleton claw-shaped and 



supporting adhesive disks. 



a. Vertebrae procoelous, ribs absent, teeth on upper 

 jaw. Family 4. Hylidce (Tree Frogs) , pp. 46 and 1 1 7. 



B. Sacral diapophyses cylindrical. (Fig. 6.) 



Vertebrae procoelous, ribs absent teeth on upper jaw. 

 (Very like the frogs, except for the arciferous shoulder- 

 girdle.) 

 Family 5. Cysiignatlidce (Lithodytes, etc., pp. 45 and 163). 



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