Dr. A. Giinther on the Geographical Distribution of Reptiles. 227 



The genus Trigonocephalus^ which has its focus in the Indian re- 

 gion, is curiously enough represented by a single species {T. halys) 

 in the southern parts of Siberia, reaching to the north of the Cas- 

 pian Sea. Thus, of all the genera peculiar to the Indian region, 

 Trigonocephalus advances furthest northward, emitting moreover 

 another species {T. Blomhoffii) to Japan. 



Japan, that outpost of the Palsearctic region, is not in the same 

 way peopled with Palaearctic snakes as we find it with Palsearctic 

 forms of other classes of the animal kingdom. As to its Herpeto- 

 logy in general, it is truly a debateable ground between the Palseo- 

 tropical and Indian Amphibio-faunse : but as regards the Ophidiay it 

 belongs entirely to the Indian region ; for the present, at least, we do 

 not know one Japanese snake which is also found in the Palsearctic 

 region, or even only belonging to one of its peculiar generic forms. 



II. Ethiopian or Western Palceotropical Region (Regio^Ethiopica). 



Characteristic forms. — Hortulia, Sansinia, Pelophilus, CasareOy 

 Calabaria. Homalosoma, Psammophylax, Heteronotus, Prosymnay 

 Meizodon, Psammophis, Dasypeltis^ Bucephalus^ Hapsidophrys, 

 Langahtty SimocephaluSy Lamprophis, Alopecion, Lycophidion, Me- 

 toporhina, Boodon, Holuropholisy Naja haje, Cyrtophis, Elapsl 

 hygice, Bendraspis, Causus, Sepedon, Atractaspis, Clotho. 



Forms common to other regions. — Philodryas, Chrysopelea^ 

 Ahcetulltty DryophiSy Leptodeira, Dipsas, Dipsadoboa. 



We now enter a tropical region, and immediately find forms of 

 gigantic magnitude, vast variety and vivacity of coloration, and a 

 great multiplication of the number of generic forms and species, al- 

 though only the southern part of this truly continental region has 

 been examined in a satisfactory manner : it is not many years since 

 the borders of Western and of part of Eastern Africa were ex- 

 plored ; and the great advance of zoological knowledge, produced 

 by this first search, promises the most extensive results to those 

 daring attempts to cross a continent which, instead of being a con- 

 tinuous burning desert, contains a new world of vegetable and animal 

 life. An enumeration of the reptiles of Western Africa, by Dr. Gray 

 (P.Z.S. 1858, p. 155 et seq.), shows how greatly our knowledge of 

 the Herpetology of that country has been enlarged in the course of 

 a few years. Therefore I hope that the ratio here given of the geo- 

 graphical area and distribution of the Ophidians will only be a proof 

 of the distance between our present knowledge and that of the coming 

 decennium. Taking the area of this region at 12,000,000 square 

 miles, and the number of species of Snakes contained therein at 

 80, we have on an average a single species to every 150,000 square 

 miles, or 2^ species to the same area for which we found only one in 

 the Palsearctic region. 



The number of Colubrina is again predominant, but is to that 

 of the Boina only as 8 : 1, and to that of the Viperina as 1 1 : 1 ; the 

 proportional number of the Boina therefore is increased, that of the 

 Viperina diminished. We must observe, first, as a peculiarity of 



15* 



