214 ON THE GEOGRAPHICAL 



crtod on the development of the shield and its edges : (this 

 race forms the genus Kinnyxis of Bell.) We shall, in the 

 last place, make mention of a no less curious difference 

 between the Em^^s, found at the Cape, in Senegal, and in 

 Madagascar : we may regard the Emys galeata of the Cape 

 as the typical form, being one of the best characterized 

 species of the genus : this Emys is replaced in Abyssinia by 

 the Emys Gehafie of RiippELL, which differs from it only 

 in some slight but constant characters.* At Madagascar 

 we see, instead of these two varieties, a different race, 

 tlic Sternothoerus nigricans ; which, though modelled on 

 the same type, is constantly distinguished from its repre- 

 sentatives bv a more heavv form, a shield less broad, and a 

 cuirass ])artially moveable. "f In recapitulating Avliat we 

 have said on the influence of climate on the animals of 

 Africa, and thence deducing general principles, we arrive 

 at this result, that the difference among animals, which 

 mutually represent each other in Southern and Northern 

 Africa, often resolves itself into a development of certain 

 ])arts more or less complete, and into a diversity of colour ; 

 those inhabiting the latter regions ordinarily exhibit a 

 livery of yellow or pale grey, — a colour most suitable for 

 animals inhabiting those desert places,J and which I would 

 willingly name the Colour of the Desert. The limited state 

 of our knowledge respecting the animals of Africa in gene- 

 ral does not permit us to give an exact table of the geo- 



* The characters are confined almost wholly to slight differences in 

 the form of the pieces of the cuirass ; a difference so frequent in Che- 

 loniaus. 



t I hope that I have shewn in my work on the C'helonians, inserted in 

 the Fauna of Japan, the small importance of the characters drawn from 

 the mobility of the cuirass, and demonstrated that very often this character 

 is purely accidental, or the effect of age. In every case, and adopting even 

 the specific difference of this last species of Emys, I believe that we should 

 destroy the natural affinities, if we elevate this animal from an isolated 

 character to the rank of a species, and thus separate it from its African 

 representatives. We may state, that this Emys is to its representatives, 

 what the Emys Pennsylvanica is to the Emys scorpioidea of Surinam. 



X As for example, most of the Antelopes of the North of Africa, the 

 numerous species of Foxes of those countries, the Dipsas, the Hares, 

 and several Gnawers ; besides a great number of birds and of reptiles, as 

 the Agami of the Desert, the Cameleon, the Eryx. the Cerastes, &c. 



