Dr. A. Giinthei- on the Geographical Distribution of Reptiles. 315 



tiou of this genus is far from being known. Respecting Cystignathus, 

 see the notice given in the sixth Region. Finally, Corniifer and 

 Plutymantis respectively are known by two species, one of which be- 

 longs to islands of the Indian Archipelago, and the other to some of 

 the Pacific. Thus the Brat rachio- fauna of this region, though offer- 

 ing well-distinguished generic forms, does not exhibit peculiar, ge- 

 neral characters as a whole, such as we found to be the case with 

 the Snakes. At present there is not known one Batrachian from 

 New Zealand. 



V. Nearctic Region. 



Characteristic forms. — Scaphiopm, Acris, Pseudacris, Notophthal- 

 mus, Taricha, Xiphonura, AmJjystoma, Cylindrosoma, Besmogna- 

 thus, Desmodactylus, Batrachoseps, SpelerjJes, CEdipus, Ensatina, 

 Axolotes, Protonopsis, Amphiuma, Menobranchus, Siren, Pseudo- 

 branchus. 



Forms common to other regions. — Cystignathus, Engystoma. 



Schlegel, by trying to establish parallels between North and South 

 America, was, I think, unfortunate in looking for respective repre- 

 sentatives of both regions : parallels may be established between the 

 Palaearctic and Nearctic region which are far more true and interesting. 



If we allow 20 species of Anura and 50 of Urodela for this 

 region, we have on an average one species to every 90,000 square 

 miles, or about three species for the same area for which we found 

 only one in the Palaearctic region. This greater abundance is due 

 to a greater number of Anura as well as of Urodela ; but if the 

 Nearctic region has three times as many Anura as the Palse- 

 arctic in proportion to its area, it yet produces four times as many 

 Urodela. 



By repeated examinations of a great number of specimens I have 

 convinced myself that the North American frog, called Rana sylva- 

 tica, does not form a distinct species from the Rana temporaria of the 

 Old World. It is true that there may be found more differences than 

 those of colour only, by examining a few specimens (for instance, 

 in the size of tympanum) ; but if we look to a greater number of 

 specimens, and compare them especially with those from the eastern 

 parts of iVsia, even those differences will be found to be levelled. 

 Among those species which are the most common, we always find 

 the greatest variations in form and colour. Among the European 

 specimens themselves were found greater differences than those be- 

 tween European and American ones ; and naturalists were induced 

 to establish several species even for the European forms. The ex- 

 tremes of the variety Rana oxyrhina might be taken at the first 

 glance for Rana esculenta ; but on comparing them with other spe- 

 cimens of the same locality, we soon come to the point where it is 

 impossible to decide to what form the specimen belongs. In like man- 

 ner any naturalist, before whom might be placed one of the above- 

 mentioned specimens from Eastern Asia, would be at a loss to de- 

 termine whether it were from the Old World or from the New. But 

 are we at liberty to separate species or genera, only according to the 

 soil where the beings are born, without finding suflficient external or, 



