RANA. 



273 



to draw up the following key, which is imperfect only 

 in so far that Forms 2 and 3 are not distinguished 

 from each other in an absolute manner; this difficulty, 

 however, cannot be overcome, as the two forms do 

 run completely into each other, and future investiga- 

 tions may even render their separation unadvisable. 



Metatarsal tubercle. 

 Heels overlapping. 1. ridibunda. 

 r2. typica. 



No f 



dorsal i tt , 



Heels not over- 



2i-4^ • 91-l*i f 



folds. , 



lapping. 



Dorsal folds 



-v o. lessonse. 

 . v4. chinensis. 



en =H 



O O 



The fourth form, being confined to Asia, will not be 

 further dealt with in this work. 



Fig. 100. 



Lower views of feet : — A. Var. ridibunda. B. Forma typica. 

 C. Var. lessonse. D. Var. chinensis. 



Var. RIDIBUNDA. 



Inner metatarsal tubercle small, blunt, feebly pro- 

 minent, its length 2^ to 4 times in the length of the 

 inner toe measured from the tubercle, and 9^ to 14 

 times in the length of the tibia ; when the limbs are 

 folded at right angles to the rhachis the heels over- 

 lap ; tibia as long as, or slightly shorter than the foot 

 measured from the outer metatarsal tubercle. The 

 tibio-tarsal articulation reaches the eye, the tip of the 



T 



