1891.] RACES OF RANA ESCULENTA. 377 



large or small, blunt or compressed. The length indicated in the 

 measurements below is the basal, i. e. taken along the attachment 

 of the tubercle to the foot ; the length of the first toe, given for 

 comparison, is taken from the tubercle ; and the length of the 

 tubercle is also compared to the length of the crus or tibia measured 

 in the flesh. 



2. The comparative length of the tibia to the thigh ; this is 

 shown by pressing the two close together and maintaining the tibia 

 at right angles to the axis of the body ; the tibial extremity is then 

 found to overlap, to meet or to fail to meet its fellow placed in the 

 same position. Only in form 1 do they overlap *, and this character 

 alone differentiates it from the three others. 



3. The presence or absence of short glandular folds along the 

 back, in addition to the glandular dorso-lateral fold. The presence 

 of these folds differentiates form 4 from the three others. 



4. The presence or absence of bright yellow pigment on the 

 lumbar and post-femoral regions. This pigment is constantly 

 absent in form 1, and very seldom in form 2. The character 

 unfortunately cannot be made use of with spirit-specimens. 



By means of these characters we are able 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 one another, and future investigations may even 

 render their separation unadvisable. 



/Heels overlapping. 1. ridibunda. Met. tubercle 2^-4 ' 



No dorsal J (2.tyjdca. „ 2-3 



^°^^'' ' S^^^^"°^ °^«'-J3.teo«<5. „ U-2 



lappins 1 II a ■" 



I lapping 



U- nig 



Dorsal folds yi. 7iiffro7naculata. „ 1-1 



l|y 



^ 9^-14 ^ d 



Jf 7-10 



■« a 5-8 



o 



5-8 J a 



Other characters have been added to complete the definitions. 



In the following tables a complete list of the specimens in the 

 British Museum is given, together with measurements taken from in- 

 dividuals from various localities. In these measurements the figures 

 in column 1 give the length, in millimetres, from snout to vent ; in 

 column 2, the length of the tibia ; in column 3, the length of the 

 foot measured from the outer metatarsal tubercle to the end of the 

 fourth toe ; in column 4, the length of the inner toe ; and in column 

 5, the length of the inner metatarsal tubercle. 



The specimens enumerated are but a portion of the material 

 studied, a picked series, in which consequently abnormal specimens, 

 i. e. such as fit least well in the technical definitions, are in greater 

 proportion than in collections made without discrimination. The 

 number of specimens in the Museum is also greater than appears 

 from the figures, as I have abstained from counting in any case 



^ As in the various species of the temporaria-grou'g, all of which, however 

 long or short the hind limbs, possess this character. 



