666 MR. G. A. BOTJLENGER ON THE [JunelG, 



3. A Description o£ the German River-Frog {Rana esculenta, 

 var. ridibunda, Pallas). By G. A. Boulenger, P.Z.S. 



[EeceiTed June 4, 1885.] 



(Plate XL.) 



When I received a year ago a larp;e number of Rana escvlenta 

 from Berlin, I was so struck by tlie differences they pi'esented that 

 I had no hesitation in regarding them as of two distinct races or 

 subspecies, and I bestowed upon the one which was new to me, and 

 to which attention had previously been called by Prof Pfliiger ', the 

 name of R. fortis. As I had not then sufficient material to establish 

 a comparison with all the forms which had already been named by 

 various authors, this seemed to me the best course, my object being 

 to draw immediate attention to the remarkable fact of two distinct 

 closely allied forms occurring in the same localitv, reserving for a 

 future occasion an investigation into the chaotic synonymy. I have 

 since constantly been amassing material; and I think I may flatter 

 myself on having now before me the finest and largest series of 

 specimens of R. esculenta with accurate localities which has ever 

 been brought together. Unfortunately, the more specimens I 

 examine, the more difficult the subject appears ; and I should not 

 think of attempting at present a general revision of the races of this 

 widely distributed species. It is evident that under the name Rana 

 esculenta a number of forms are thrown together, the extremes 

 of which are as distinct as many we are accustomed to regard 

 as valid species ; but as they are linked together by numerous 

 insensible gradations, it is best to regard them as subspecies. 



The great number of specimens, both alive and in spirits, which have 

 lately passed through my hands, have more and more strengthened 

 my belief in the constancy of the characters upon which I have based 

 the distinction of R. fortis and R. esculenta ; but tliey have also 

 convinced me that the name R. fortis should be cancelled in favour 

 of the name R. ridibunda, Pallas. 



My object at present being merely to give a detailed account of 

 the recently discovered German Frog, I will leave aside all further 

 material in order to avoid confusion, and all that is said of R. escu- 

 lenta for comparison applies only to Germau specimens. The 

 following description is based on the examination of about 130 

 specimens of R. ridibunda, of which six are from Prague, the rest 

 from Berlin. 



Rana esculenta, var. ridibunda. 

 Rana ridibunda, Pallas, Reise, i. p. 4.58 (1/71). 

 Rana cachiniians, Pallas, Zoogr. Ross. -As. iii. p. 7, [tl. i. figs. 1, 2 

 (1831); Eichwald, Faun. Casp.-Cauc. p. 126, i)l. xxx. (1841'). 



^ Ai-ch. f. Physiol, xxix. 1882, p. 67. 



