214 
ON THE OEOaRAPHICAL 
erted on the development of the shield and its edges : (this 
race forms the genus Kinnjxis of Bell.) We shall, in the 
last place, make mention of a no less curious difference 
between the Emys, 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 Buppell, which differs from it only 
in some slight but constant characters.^ At Madagascar 
we see, instead of these two varieties, a different race, 
the Sternothoerus nigricans ; which, though modelled on 
the same type, is constantly distinguished from its repre- 
sentatives by a more heavy form, a shield less broad, and a 
cuirass partially moveable, f In recapitulating what 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 
parts 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,! 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- 
lonians. 
t I liope that I have shewn in my work on the Chelonians, 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. 
i As for example, most of the Antelopes of the North of Africa, the 
numerous species of Foxes of those countries, the Dipsas, the Ilare^, 
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. 
