Ornithology of Northern Africa. 155 
to any one who has sailed through the Straits of Gibraltar, that 
it is needless to imagine that it had any foundation in historic 
memory. If we might here hazard a conjecture, it would be that 
the same convulsions and upheavals*, which at the close of the 
tertiary epoch indented the southern coasts of Europe, at the 
same time drained the ocean, which up to that time had rolled 
over the plains of the Sahara, and submerged the low-lying 
lands which probably united the Canaries and Madeira to the 
main land. The natural history of these islands is so essen¬ 
tially European as to point to an identical centre of creation. 
We may then imagine that towards the close of the later geo¬ 
logical epoch, Barbary was a vast peninsula linked to Europe 
by Gibraltar, and washed on the south by the ocean of the 
Sahara, on the north by the inland lake which is now the Medi¬ 
terranean. 
It is to be observed, also, that the geological character at once 
changes, when, leaving the southern slopes, we enter the Sahara. 
Upon the surface of the tertiary deposits and nummulitic lime¬ 
stone we come to masses of granite, quartz, and other igneous 
formations, with numerous rounded pebbles and large gravel, 
bearing all the marks of an ancient sea-bed, besides the extraor¬ 
dinary mountains of pure rock-salt, which in various places rise 
suddenly from the limestone. During my rambles in the Sahara 
the only true fossils I found were of a species of Chama, im¬ 
bedded in the cliffs, though abundant fragments of tertiary 
shells lie scattered among the sands. 
Such being the physical geography of North Africa, we need 
not be surprised at finding its Flora and Fauna closely approxi¬ 
mating to those of Europe, i. e. if we take, as the limits of Bar¬ 
bary, the foot of the southern slopes of the Atlas. Towards the 
end of the last century Desfontaines carefully explored its Flora, 
and described it in his well-known work f Flora Atlantica/ The 
additions made by Mr. Munby and others, subsequently, have 
raised the list of Desfontaines to about 2000 indigenous species. 
Among these I can scarcely find a single genus which is not 
represented in the Flora of Spain, Sardinia, or Sicily, with the 
* I once found on the Barbary coast a raised tract composed of masses 
of tertiary shells, 250 feet above the present Mediterranean level. 
