Robinson 1965), but this is by no means supported by the evidence. Some 

 of this evidence I am presenting here for the first time. 



In 1966 I effected a reconstruction of most of the posterior two-thirds 

 of the vault of the cranium (Figure 20). The reconstruction includes the 

 2 parietals and the occipital (as far forward as the posterior intra-occipital 

 synchondrosis, which has, of course, long since ossified). Parts of the frontal 

 and of the right temporal bones articulate with the rest, but for purposes 

 of computing the endocranial volume they have been omitted from the 

 reconstruction. Thus, the proportion of vault available for the making 

 of a partial endocast is greater than was the case with the type specimen 

 of H. habilis (where no occipital was included). 



Within the incomplete reconstructed vault, R. J. Clarke made a partial 

 endocranial cast. Anteriorly, this was smoothed off flush with the plane of 

 what I recorded in my notes as "an apparent portion of the coronal suture." 

 Inferiorly, the notch in the squamosal margin of the parietal was carried 

 right across the basal surface of the endocast, as was done in the making of 

 the part-endocast of Old. Horn. 7. Postero-inferiorly, the plane of truncation 

 of the endocast passed just behind the foramen magnum and traversed the 

 impression of the cerebellar hemisphere on each side. The endocast thus in- 

 cluded all that part of the endocranial cavity cut off beneath the biparietal 

 tunnel, together with that portion continued within the concavity of the 

 squama occipitalis. 



Comparable truncated part-casts were made of the endocasts of Old. 

 Horn. 5 (A. boisei) and of Sts 5 (A. africamts). The casts were then varnished 

 with shellac and their volumes determined by volumetric displacement of 

 water, 6 times each. 



The 6 estimates of the part-cast of Old. Horn. 13 yielded values of 389, 

 389. 391. 393. 394. an d 394 cc - "The mean of the 6 readings was 391.67 c.c. 

 The 6 readings for Sts 5 ranged from 292 to 295 c.c. and gave a mean value 

 of 293.67 c.c. This amounted to 61.2 per cent of the estimated total of 480 

 c.c. (or 60.6 per cent of Holloway's estimated total of 485 c.c). The 6 read- 

 ings for Old. Horn. 5 ranged from 322 to 328 c.c, with a mean of 325.5 c.c. 

 This amounted to 61.4 per cent of the estimated total of 530 c.c 



Thus, the 2 specimens used as analogues yielded ratios of 61.2 (or 60.6) 

 and 61.4 per cent. When the value for the part-endocast of Old. Horn. 13 is 

 brought up to 100 per cent on this basis, capacities of 640.0 and 637.9 c.c. 

 are obtained, or, in round figures, 638 to 640 c.c. The midvalue of the 2 

 estimates is 639 c.c. Thus, the estimate for the paratype of H. habilis is only 



73 & 



