8 RANID, 
they might just as well be referred to the one as to the other. 
Besides, the well-known R. macrodon, R. kuhlii, and others have the 
tips of the toes dilated into very distinct disks, much more so than 
several species hitherto referred to Hylorana. 
I have therefore come to the conclusion that, with regard to the 
species of this group, the difference in the shape of. the fingers and 
toes cannot be used as generic character, as we should be obliged to 
place far apart species which, in all other respects, are very much 
alike. This conclusion was foreseen by Mr. Cope some twelve 
years ago*, Stating that Hylorana stands very near Rana, he 
observes that “it is only to be distinguished from it generically, 
without the interposition of any possible form which would not 
unite them. The T-shaped phalange in some Hylorane is so weak, 
while the expansion of the tip of the same in Rana temporaria and 
others is so distinct, as to render the permanent distinction of the 
two genera a mere matter of future discovery.” 
It has long been believed that the shape of the tips of the fingers 
and toes is always in immediate relation with the mode of life of 
the Frog; but it now appears that several platydactyle species 
are entirely terrestrial or aquatic, not arboreal. 
Had not the species been so numerous, I would have hesitated to 
separate Rana from Rhacophorus, which I characterize by the 
presence of a more or less developed web between the fingers. 
Though both genera pass into each other and constitute an un- 
interrupted series of species, I think that division convenient, it 
being easy to ascertain whether the fingers are quite free or 
webbed. 
As characterized by Dr. Giinther and other authors, the genus 
Pys«icephalus, Tschudi (Tomopterna (Bibr.), Gthr.), is supposed to 
differ from Rana by a stouter habit, and especially by the great 
development of the inner metatarsal tubercle, which is large, 
compressed, shovel-like, as in Pelobates, Scaphiopus, &e. Had all 
the species of Pyaicephalus a “large and thick head,” and all 
the species of Rana the ‘metatarsal tubercle blunt,” it would 
certainly be very natural to separate these two forms ; but such is 
not the case, and it will be shown that the genera Pya«icephalus 
and Rana can no longer be distinguished. 
Prof. Peters established many years ago a new genus, Hoplo- 
batrachus, for a Ceylonese Frog which, according to him, is exactly 
intermediate between Rana and Pyxicephalus. This supposed new 
Frog is nothing but a variety of Rana tigrina. In this species the 
inner metatarsal tubercle is generally blunt, half as long as the first 
toe, or even less; other specimens (from Ceylon, Madras, and 
Malabar) have the tubercle shovel-shaped as in Pyw«icephalus ad- 
spersus, and about as long as the first toe; other specimens are 
intermediate. ‘These differences in the shape and size of the inner 
metatarsal tubercle do not correspond with any important character ; 
* Proc. Amer. Philos. Soc. xi, 1869, p. 168. 
