Vol. 69.J THE HUMAN SKULL, ETC. FROM PILTDOWN. 139 



that, during the post-natal life of all the existing apes, the skull 

 has at first the curiously rounded shape of the Piltdown specimen, 

 with a high frontal eminence and scarcely any brow-ridge ; while 

 as growth proceeds a postorbital constriction begins, the bony brow 

 grows forwards, the forehead becomes flattened, and the familiar 

 well-marked ape-skull is the result (fig. 8, p. 140). Our knowledge 

 of the principles of palaeontology compels us to suppose that 

 the full-grown skull in the ancestral mid-Tertiary apes was of the 

 immature rounded shape just mentioned, although we have not 

 yet been fortunate enough to discover an example ; and, during 

 the lapse of Upper Tertiary time, the skull-type in the whole race 

 of apes has gradually undergone changes which are more or less 

 exactly recapitulated in the life-history of each individual recent 

 ape. Hence, it seems reasonable to interpret the Piltdown skull 

 as exhibiting a closer resemblance to the skulls of the truly ances- 

 tral mid-Tertiary apes than any fossil human skull hitherto found. 

 If this view be accepted, the Piltdown type (fig. 9, p. 14-1) has 

 gradually become modified into the later Mousterian type (fig. 10, 

 p. 141) by a series of changes similar to those passed through by 

 the early apes as they evolved into the typical modern apes, and 

 corresponding with the stages in the development of the skull in 

 an existing ape-individual. It tends to support the theory that 

 Mousterian man was a degenerate offshoot of early man, and 

 probably became extinct ; while surviving man may have arisen 

 directly from the primitive source of which the Piltdown skull 

 provides the first discovered evidence. 



For much valuable help in studying these human remains I 

 wish especially to thank Mr. W. P. Pycraft, A.L.S., and Mr. Arthur 

 S. Underwood, M.R.C.S. 



The Associated Mammalia. 



The associated mammalian remains are well mineralized with 

 oxide of iron, and, as might be expected in so coarse a gravel, they 

 are all very fragmentarj\ 



Mastodon (PI. XXI, figs. 1, 1 a, & 1 b). — A much-rolled specimen 

 is readily identified as the cusp of a molar of Mastodon, of the 

 same type as 31. arvernensis. The outer enamel, with the charac- 

 teristic irregularities, is well preserved, and the waterworn base 

 shows the upper end of the large pulp-cavity. The cusp has three 

 apices closely pressed together, the median one being relatively 

 small and crushed between the others ; and the fossil is sufficiently 

 complete to show that it was an isolated eminence on a tooth, not 

 part of a continuous ridge. 



Stegodon (PI. XXI, figs. 2, 2 a, 3, & 3 «).— Two fragments of a 

 large Proboscidean molar, which have evidently been broken with 

 great force but are scarcely rolled, are referable to a very primitive 

 type of true elephant. One piece (figs. 2 & 2 a), in which the 



