A mutual approximation of the temporal ridges in the coronal region may be observed in the skulls of various nations. This formation is most frequent in the long-headed negro and Papuan skulls. In these cases it is generally allied with the shortness of the interval between the sides of the skull, taken in its transverse diameter (stenocephalism). In an adult female chimpanzee, the parietal bones often rise abruptly towards the sagittal suture, and in its vicinity there arises a longitudinal bony prominence, of which the sides pass gradually into the external surface of the parietal bones. The sagittal suture sometimes remains intact, and is sometimes included by this process. This produces a modified development of the so-called keel-shaped skull (_scaphocephalus_). Such a formation may be often observed in negroes and Papuans, and more rarely in the skulls of other races. The occurrence of a divided malar bone in human skulls, especially in those of the Ainos and Japanese, has been considered to be theromorphic, since it is occasionally observed in the skulls of apes.[43] I have myself, in a very few instances, found obscure traces of such a formation among anthropoids. In 1863 Boucher de Perthes found at Abbeville half of a human lower jaw deposited in a black layer of clay and sand mixed with iron, and lying on the chalk. As far as we can judge from illustrations which are for the most part imperfect, there was nothing remarkable about it except its abruptly retreating ramus (Fig. 36), but the specimen aroused great attention at the time, and it was assigned by many intelligent observers to the primitive men of the diluvial period. Unfortunately it was afterwards proved to be a gigantic imposture.[44] [Illustration: Fig. 36.--Lower jaw of Moulin-Quignon.] [Illustration: Fig. 37.--Naulette lower jaw.] [Illustration: Fig. 38.]