Vol. 70. MEDIAN PLANE OF THE PILTDOWN SKULL. 97 



of the fossil shows that this ridge corresponds to the place where 

 the two halves of the frontal bone originally came together at the 

 metopie suture. Although it is not uncommon to find in the 

 crania of primitive man a metopie crest upon the outside of 

 the frontal hone (that is, at the spot marked cr. in fig. 6, p. 96), 

 an endocranial metopie crest is of much rarer occurrence. It is 

 found, however, in the neighbourhood of the bregma in the Neander- 

 thal skull ; and there is no doubt of its identity in the specimen 

 now under consideration. 



Mr. Frank Barlow called my attention to the fact that, if this 

 fragment be looked at from in front (or a transverse section of 

 a cast of it, tig. b', be studied), the curve of the frontal bone 

 describes a gentle sweep above the temporal ridge (T), which 

 reaches its summit {cr.) directly above the endocranial ridge (>•), 

 beyond which it begins its descent, showing that it has crossed 

 the middle line to the right side. This affords independent 

 corroborative evidence of the correctness of the determination of 

 the median plane (Jf). 



My friend Prof. J. T. Wilson, F.B.S., has pointed out that the 

 inclination of the floor of the anterior cranial fossa (fig. 6, FL) 

 provides further evidence in support of my contention. For, if 

 the bone be tilted laterally to even a small extent, the floor would 

 become inclined at an angle such as is unknown in any skull, 

 whether human or simian. 



If the median line thus determined in the region of the bregma 

 (tig. o, p. 95) is prolonged backwards, it cuts the posterior corner of 

 the parietal in the neighbourhood of the lambda (fig. 5). Inde- 

 pendent evidence, derived from (a) the study of the manner of 

 articulation of the left parietal and temporal bones, and their 

 relationship to the occipital ; (b) the texture of the endocranial 

 surface of the bone along the line M; (c) the fact that the trans- 

 verse section of the supralambdoid flattening (O) is horizontal 

 only when the bone is placed as it is represented in the diagram ; 

 and (<7) the situation and relations of the parasagittal crest (P), — 

 all confirms the accuracy of the identification of the median plane 

 as it is represented in fig. 5. 



If the fossil be held in a certain light, a series of depressions ($') 

 can be detected, which closely resemble those found in the supra- 

 lambdoid region of skulls (such as the Neanderthal ealvaria) where 

 the sagittal suture has recently become closed. The suggestion 

 is that the posterior end of the sagittal suture conformed to the 

 pattern represented at >S" in fig. o, and had recently closed when 

 the Piltdown man met his death. This may occur in modern man 

 at any age between 80 and 40 years — although, in rare instances, 

 it may happen before 130, or (more often) be delayed beyond 40. 

 There are reasons for believing that this individual was a young 

 adult, and possibly a female : for the features that present secondary 

 sexual characters in modern skulls are quite indefinite in the*c 

 fragments. 



Q. J. G. S. No. 277. h 



