ARCHIVUM ZOOLOGICUM 
N« 4. 
Editum est die 15. XII. 1909. 
Vol. I. 
Description of a hybrid of Rana esculenta L. and Rana 
ridibunda Pall. 
By Dr. S. J. Bolkay. 
On Ihe May 1907 I found at Budapest, (on llie Lagymanyos) a frog, wliich 
al first sight I took for a Rana esculenta L. Until quite recenlly I regarded this 
specimen as an Edible Frog, but as I examined it more closely il became clear 
to me that I had to do with a hybrid of the R. esculenta L. and R. ridibunda 
Pall. Considering the fact that the R. esculenta and R. ridibunda live together on 
the Lagymanyos, my supposition of the mentioned specimen heing no olher than 
a hybrid of these two species seems quite natural. 
This supposition of mine has been Ihoroughly juslified hy a more attentive 
examination the result of which I find all the more necessary to communicate as 
the Hungarian zoological literature, up to now, does not menlion any such a case 
of a hybrid of R. esculenta and R. ridibunda. 
My specimens figure on the whole, greatly resemhles that of the Edible Frog; 
the tip of its snout is hovvever more pointed; the inter-orbitale space is equal to 
the two thirds of an upper eyelid, and two thirds of the distance between the 
nostrils. The glandular lateral folds are comparatively very broad and a little wider 
than the diameter of an upper eyelid. The tibio-tarsal Joint reaches the middle of 
the tympanum. Heels do not meet when hind limbs are bent at right angles to 
the axis of the body. 
The inner metatarsal tuhercle (lig. 1 and In) is small, oval, soft and a little shorter 
than the distance between it and the first subarticular tuhercle on the hallux, it 
is surprisingly similar to the inner metatarsal tuhercle of the Rana agilis Thom. 
The subarticular tubercles are well developed, and strongly prqjecting. 
On the base of the fourth (longest) toe there is a small hut strongly projecting 
outer metatarsal tuhercle. 
