226 W. F. KIRBY, F.E.S. 
that at no very remote period, geologically speaking, the 
Mediterranean only existed in the form of two or three land- 
locked lakes, continued by a series curving north-east through 
Asia to the Arctic Ocean. At the same time, the country 
now occupied by the Sahara Desert was probably covered by 
a broad sea, similar to the Mediterranean, and possibly open 
on the west, and landlocked on the east in the same way. 
Hven now, many of the lakes of Central Asia are rapidly 
drying up, and thus the geographical changes in the character 
of that country are still in progress. 
It will, perhaps, be better to consider the relationship of 
the various Northern Faunas to Africa, before discussing the 
character of the more characteristic African Faunas. 
In the first place, the strictly Northern Fauna, including 
the Alpine, hardly touches North Africa at all. Many of our 
most characteristic Central Huropean insects become mountain 
insects in the extreme south of Hurope, and many others do 
not cross the Mediterranean. ‘Thus, our familiar Peacock 
Butterfly (Vanessa Io), though common from Ireland to Japan, 
is a great rarity in Sicily, and is quite unknown in North 
Africa. Two of the most characteristic of the Huropeo- 
Asiatic Alpine genera of butterflies, Parnassius and Hrebia, are 
each represented by a single species only in the mountains of 
South Spain, and I am not acquainted with a single repre- 
sentative of any truly Alpine species which occurs in the 
mountains of North Africa, though the genus Hrcbia is 
replaced in Southern Africa and Madagascar by the closely- 
alhed genus Pseudonympha. The genus Colias, which includes 
the Clouded Yellows, is represented in Northern Africa by the 
two common Huropean species C. Hdusa and OC. Hyale. 
CO. Kdusa occurs throughout the deserts of North-Hastern 
Africa, but disappears in Central Africa, though in Southern 
Africa we meet with it again under the slightly modified form 
of C. Hlectra. And, what is perhaps more singular, C. Hyale, 
though less widely distributed in Northern Africa than 
C. Hdusa, likewise reappears in South Africa, where, however, 
it is far from common. And here I may say that I believe that 
the reputed occurrence of our common Small Cabbage White 
Butterfly, Pieris Rape, on the West Coast of Africa, requires 
confirmation. Hewitson, indeed, received two specimens 
from thence ; but I am inclined to think that they were either 
mixed with African species in error, or else were simply 
derived from some missionary’s garden. 
The disappearance of the Northern and Alpine Huropeo- 
Asiatic Fauna renders the Fauna even of South Hurope much 
poorer than that of Central Kurope, and that of North Africa 
