66H 



MR. G. A. BOTJLENGER ON THE 



[June Hi, 



implies a greater length of the tibia proportionally to the femur in 

 J{. ridibunda. The foot is fully wthbed ; its length, from the outer 

 metatarsal tubercle to the end of the fourth toe, equals half the 

 distance from the vent to t!ie nostrils or the tij) of the snout, or a 

 little more. The subarticular tubercles of the toes as well as of the 

 fingers are rather small and feebly prominent. The inner metatarsal 

 tubercle is elliptical, blunt, much less prominent than in the typical 



b c 



Heads of Hand cscukuta. 



B. esculenta ; it is also smaller compared with the inner toe, its 

 length seldom equalling, and never exceeding, its distance from the 

 subarticular tubercle of that toe. In the typical form the meta- 

 tarsal tubercle is always more prominent, more or less stroni;lv 

 compressed, frequently crescentic in shape ; its length at least equals, 

 and usually considerably exceeds, its distance from the subarticular 

 tubercle. However, the length of the metatarsal tubercle is, like all 

 chaiacters, subject to a certain amount of variation ; the smaller 

 variety of the typical R. esculenta, which occurs along the Rhine, 

 has usually the tubercle larger than in the larger variety of the same 

 form as occurring in Berlin and elsewhere, and to which Rdsel's 

 hana viridis belongs. It is a fact that a graduated series may be 

 formed from the It. ridibunda with very small tubercle to the 

 R. esculenta with very large tubercle, and such a series is represented 

 in tiie accompanying figures (Fig. 2, p. 669)- 



The skin of the back and hind limbs is more or less warty, seldom 



