Posidonius, who himself divides the earth into zones, tells us that “five is the number best suited for the explanation of the celestial appearances, two of these are periscii,631 which reach from the poles to the point where the tropics serve for Arctic Circles; two more are heteroscii,632 which extend from the former to the inhabitants of the tropics, and one between the tropics, which is called amphiscius,633 but for matters relative to the earth, it is convenient to suppose two other narrow zones placed under the tropics, and divided by them into two halves, over which [every year] for the space of a fortnight, the sun is vertical.”634 These zones are remarkable for being extremely arid and sandy, producing no vegetation with the exception of silphium,635 and a parched grain somewhat resembling wheat. This is caused by there being no mountains to attract the clouds and produce rain, nor any rivers flowing636 through the country. The consequence is that the various species637 are born with woolly hair, crumpled horns, protruding lips, and wide nostrils; their extremities being as it were gnarled. Within these zones also dwell the Ichthyophagi.638 He further remarks, that these peculiarities are quite sufficient to distinguish the zones in question: those which are farther south having a more salubrious atmosphere, and being more fruitful and better supplied with water.