other hominoid distributions, including that of another hylobatine sample, 

 the siamang, that it was strongly suspected a typographical or other error 

 had crept into the data tabulated for gibbons in Vallois's paper (1954). 



In a letter in response to my inquiry, M. Vallois has indeed indicated 

 that the published mean of 89.3 c.c. was erroneous and that the mean 

 value should be 94.3 c.c. This figure, he stated, was based on Schultz's 

 (1933) data for 77 gibbons of both sexes, coupled with Vallois's own data 

 for 9 gibbons of both sexes. Even the revised mean of 94.3 gives an 

 unusually asymmetrical distribution if the minimum and maximum values 

 have been correctly cited. However, reference to Schultz's original (1933) 

 paper revealed that the range cited by Vallois (1954) was not correct. 

 Schultz's (1933) data for 77 gibbons of both sexes show a range of capacities 

 from 70 to 136 c.c, whereas Vallois's stated range for 86 gibbons (which 

 included Schultz's 77) was 87 to 130 c.c. It is possible that the shorter 

 range represents that of only the 9 gibbon capacities that Vallois himself 

 added to Schultz's 77 capacities. The total range culled from Schultz (1933) 

 is much more symmetrical than Vallois's range. If we accept Vallois's new 

 mean for the 86 capacities, namely 94.3 c.c, then the minimum value 

 (70 c.c.) is 24.3 c.c, or 2.2 estimated S.D.s, below the sample mean, while 

 the maximum value (136 c.c) is 41.7 c.c, or 3.8 S.D.s, above the sample 

 mean. If we follow Schultz's mean of 97.5 c.c. for 77 gibbons of both sexes, 

 the minimum capacity (70 c.c.) is 27.5 c.c, or 2.5 estimated S.D.s below 

 the mean, while the maximum value (136 c.c.) is 38.5 c.c, or 3.5 estimated 

 S.D.s, above the mean. This represents a positively skewed distribution, 

 comparable with that for the gorilla combined-sex sample shown in Table 

 12. 



A serious objection to using either Schultz's 77 or Vallois's 86 gibbon 

 capacities in Tables 4, 9, and 12 is that their samples are made up from 

 several different hylobatine species, whereas the figures for each of the 

 other hominoids cited are for samples drawn from a single species. Thus, 

 Schultz's 77 gibbon capacities comprise 28 of Hylobates lar, 21 of H. agilis, 

 10 of //. cinereus, 9 of H. pileatus, 6 of H. concolor, and 3 of H. hoolock 

 (but exclude 10 of H. klossii). 



Hence, the figures based on these 77 crania and on Vallois's 86 crania 

 have here been discarded. To elucidate the question further, I approached 

 Dr. A. Schultz, and he very kindly provided me with the original, unpub- 

 lished raw data for the series described in his 1944 monograph. These 

 data are the cranial capacities of 95 male and 85 female fully adult, wild 



5i K 



