104 ESSENTIALS OF ZOOLOGY 



number of digits; position of teeth; presence or absence of a naso- 

 labial groove; plantar tubercles; shape of vertebrae; form of cranial 

 bones and cartilages; presence or absence of lungs; presence or 

 absence of ypsiloid cartilage; and other factors. 



Some characters used in classifying adult frogs and toads are: 

 color markings; length of body and of hind limb; shape of head; 

 nature of skin; presence or absence of parotoid glands and their 

 shape; presence or absence of tympanum; presence or absence of 

 cranial crests and their shape; presence or absence of teeth and 

 their situation; the shape of the vertebrae; shape of the sacrum 

 and pectoral girdle ; shape of pupil of the eye ; presence or absence 

 of adhesive discs at the ends of digits ; and other characters. 



The student interested in classification and identification of species 

 should consult appropriate keys for the various groups of Amphibia. 



A List of Families of the Amphibia in the United States 



The ranges cited below are not exact but give an idea of the dis- 

 tribution of the genera. 



Order Caudata (Tailed Amphibians) 



Suborder Cryptohranchoidea 



Family Cryptobranchidae 



Cryptobranchus alleganiensis (1 species). This so-called "hellbender*' 

 ranges from the eastern states west to Iowa, south to Louisiana. 



Suborder Ambystomoidea 



Family Ambystomidae 



Amby stoma (about 12 species). Common species in the Southwest are: the 



Tiger salamander (A. tigrinum) ; the Texan salamander (A. texanum) ; 



and the Marbled salamander (A. opacum). 

 Dicamptodon ensatus (1 species). Washington to Southern California. 

 Bhyacotriton ■ olympicus (1 species). Olympic Mountains, Wash. 



Suborder Salamandroidea 



Family Salamandridae 



Triturus (about 3 species in the United States). The common newt of the 

 Southwest is Triturus viridescens louisianensis. The other species repre- 

 sented is T. meridionalis. 



Family Amphiumidae 



Amphiuma (2 species). A. tridactylum, the three-toed congo eel, ranges 

 from northern Florida to eastern Texas. 



Family Plothodontidae 



Gyrinophilus porphyriticus (1 species). Eastern states west to Kentucky, 

 south 10 Georgia. 



