tare of the vocal organs. Bufo vulgaris of the old World i- repre- 

 Beated in North America by />'. lentiginosus, in South America by 

 /;. ckilensis — all sufficiently distinguished by the Btructure of the 

 skull. Hyla arborea has its representative in //. euphorbiacea from 

 the table-land of Central America. Thus we find one <>f our most 

 common Anura t » > be the same in the New World, and three others 

 represented by closely allied species. Our fifth common species, 

 Bombinator igneus, is a more local species, and bas no representative 

 in North America. No species of the Urodela is common to both 

 regions, not even a genus; but in both we have not only such 

 genera as are assigned by their structure either to living in water of 

 on land, but also those intermediate forms which cannot be justly 

 brought to one or the other category. Among the Urodela with 

 free gills or gill-openings, Sieboldia exhibits at least such similarities 

 with Menopoma, and Proteus such with Menobranehus, that they 

 may he well considered as representing one another in the two re- 

 gions. Thus we Hud the Nearctie and I'ahearctic regions nearer 

 allied in respect to Batrachio-fauna than they are to any other. 



Cystignathus and Engystoma severally exhibit one species in the 

 southern parts of North America, those gensra belonging, in fact, 

 to the Tropics. 



VI. Neoti'opic Region. 



Characteristic forms. — Pipa, Pseiidis, Calyptocephalus, Cyclo- 

 rhamphus, Vithecopsis, Limnocharis, Hylorhina, Pyxicephaliu, 

 tophrys, Leiuperus, Pleurodema, AJsodes, Phryniscus, Braehy- 

 cephalus, Rhinoderma, Atelopus, Engystoma, Otilophus, Elosia, 

 Crossodactylus, Phyllobates, Hyfodes, Nototretna, Opisthodelphys, 

 Trachyceph at us, PhyUomedusa, Hylaplesia, lili inophrynus. 



Form common with other regions. — Cystignathus. 



There is on the northern boundary of this region the Batrachio- 

 fauna mixed with Arctic forms, which is also the case in other parts 

 of the animal kingdom, without taking into account those auiinal- 

 which, living on mountains, find by this vertical elevation (he con- 

 dition of a more northern climate. The absence of the genus Rana 

 may he pointed out as a character of this region ; <>ne species, how- 

 ever, which I think I have recognized as R. Lc<-ont ii of (tirard, 

 reaches, together with Hyla versicolor, into the South of Mexico, and 

 i- found in localities with Bufo granulosus, Hylaplesia, and Rhino- 

 phrynus. Bufo chilensis ranges along the western coasts to Califor- 

 nia, Hut putting aside these examples, we meet, (Mi entering Mexico, 

 that Batrachio-fauna, by the abundance and peculiarity of which this 

 region i- widely distinguished beyond all the other-. Then- we 

 meet the greatest number of species of //'//" and Hyla, and those 

 peculiar tree-frogs with a pouch on the back for their progi \>\ ■. and 

 there also we meet the single representative of the Proteroglossa. 

 This region is the most productive in Batrachians, as we find the 

 Bast Indies to he in Snakes. At least 1 in specie- are known, giving 

 one species for ever) 50,000 square mile-, rather more than one- 

 half of them belonging to the Platydactyla. South America pro- 



