CLASS AMPHIBIA 



483 



these species are subdivided into several subspecies. The Southwest 

 contains a large proportion of all of these. 



Some characters used in classifying salamanders are : the presence 

 or absence of gills, either external or internal; color markings; 

 shape and appearance of body; length; number of costal grooves; 

 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. 



Some characters used in classifjdng adult frogs and toads are : 

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



Fig. 269. — Tree frog, Hyla crucifer. (Photograph by Thos. Mebane Jones.) 



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. 



The student interested in classification and identification of species 

 should consult appropriate keys for the various groups of Amphibia. 

 There is appended at the end of the book a list of references deal- 

 ing with this class of animals. 



