(FIGURE 16.--Sections of the skulls of Man and various Apes (Australian, Chrysothrix, Gorilla, Cynocephalus, Mycetes, Lemur), drawn so as to give the cerebral cavity the same length in each case, thereby displaying the varying proportions of the facial bones. The line 'b' indicates the plane of the tentorium, which separates the cerebrum from the cerebellum; 'd', the axis of the occipital outlet of the skull. The extent of cerebral cavity behind 'c', which is a perpendicular erected on 'b' at the point where the tentorium is attached posteriorly, indicates the degree to which the cerebrum overlaps the cerebellum--the space occupied by which is roughly indicated by the dark shading. In comparing these diagrams, it must be recollected, that figures on so small a scale as these simply exemplify the statements in the text, the proof of which is to be found in the objects themselves.) But if we consider the proportional size of the facial bones to the skull proper only, the little 'Chrysothrix' (Figure 16) differs very widely from the Gorilla, and, in the same way, as Man does; while the Baboons ('Cynocephalus', Figure 16) exaggerate the gross proportions of the muzzle of the great Anthropoid, so that its visage looks mild and human by comparison with theirs. The difference between the Gorilla and the Baboon is even greater than it appears at first sight; for the great facial mass of the former is largely due to a downward development of the jaws; an essentially human character, superadded upon that almost purely forward, essentially brutal, development of the same parts which characterizes the Baboon, and yet more remarkably distinguishes the Lemur. Similarly, the occipital foramen of 'Mycetes' (Figure 16), and still more of the Lemurs, is situated completely in the posterior face of the skull, or as much further back than that of the Gorilla, as that of the Gorilla is further back than that of Man; while, as if to render patent the futility of the attempt to base any broad classificatory distinction on such a character, the same group of Platyrhine, or American monkeys, to which the 'Mycetes' belongs, contains the 'Chrysothrix', whose occipital foramen is situated far more forward than in any other ape, and nearly approaches the position it holds in Man. Again, the Orang's skull is as devoid of excessively developed supraciliary prominences as a Man's, though some varieties exhibit great crests elsewhere (See pp. 231, 232); and in some of the Cebine apes and in the 'Chrysothrix', the cranium is as smooth and rounded as that of Man himself.