The deserts of North America and that of the Kalahari might more accurately be called steppes. Even in the Sahara we must distinguish between the desert proper and the steppes which surround it. To the north there are certain places, as in southern Tunisia, the Syrtes and Marmarica, where the Sahara reaches right to the Mediterranean coast. But elsewhere, particularly in the Atlas region and in Cyrenaica, where the altitude modifies the desert influences, we find steppes appearing. In considering the animal life of the Sahara, we must again be careful to avoid confusion between the desert proper and the steppes. The Sahara is a region relatively azoic in character: that is, lacking in any form of life. The truly Saharan nomads are all exclusively camel herders; and while their personal energy is extreme, one characteristic common to all tribes is numerical insignificance.