they might just as well be referred to the one as to the other. 

 Besides, the well-known R. macroclon, R. JcuhJii, and others have the 

 tips of the toes dilated into very distinct disks, mnch more so than 

 several species hitherto referred to Hylnrana. 



I have therefore come to the conchision 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 Hylorance 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 futiire 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 Rhacopliorns, 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 

 Pyxicephaliis, Tschudi {Tomoptema (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 Pelohates, Scaphiopus, &c. Had all 

 the species of Pyxicephalus 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 Pyxiaphahts 

 and Rana can no longer be distinguished. 



Prof. Peters established many years ago a new genus, Hoplo- 

 hatradms, 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 Cejion, Madras, and 

 Malabar) have the tubercle shovel-shaped as in Pyxicephahis acl- 

 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. AiHQr. Philos. Soc. xi. 1869, p. 168. 



