HuTTON. — On Moa-bones at Kapua. 631 



then the females would outnumber the males, but we should 

 expect to tind the same proportion between the sexes main- 

 tained in each locality. On the other hand, two varieties of 

 a species might, very probably, have different geographical 

 distributions or dilferent habitats. This may enable us to 

 distinguish between varieties and sexes, and to test the 

 validity of supposed species. 



In the third place, we may assume that if a considerable 

 difference in size between the sexes existed in one species it 

 existed in all belouging to the same genus; and, vice versa, if 

 there was no sexual difference of size in one species, probably 

 there was not much difference in others. Consequently, if 

 two different sizes of a species occur frequently, they are 

 probably due to sexual differences ; if, however, this only 

 occurs occasionally, it is probably due to the existence of two 

 varieties. 



Another important result of these measurements is to 

 show that of all the leg-bones the tibio-tarsus is the least 

 variable and gives the best specific characters. 



Explanation of the Diagrams. 

 "While a knowledge of the width at the extremities of the 

 limb-bones is necessary for their generic determination, the 

 specific characters chiefly depend on the length and on the 

 width of the shaft in the middle. I have therefore drawn a 

 set of diagrams showing both of these measurements and also 

 the number of bones agreeing with them, these being ex- 

 pressed by numbers in the squares ; consequently these dia- 

 grams give the length and mid-width of each of the 2,010 

 bones which I measured. An examination of them will 

 show what I mean by the bones being arranged in clusters ; 

 generally with one, but occasionally wdth two, points of 

 concentration within what I take to be a specific area. It 

 will be noticed tiiat it is only occasionally that the lines 

 defining the species are arbitrarily drawm — usually there is 

 a distinct indication of a break. My greatest difficulty has 

 been to distinguish between the leg-bones of Euryapteryx 

 crassa and those of Meionornis casuariniis. The leg-bones of 

 these two species pass completely into each other, and in 

 drawing the line of division I have been guided by the pro- 

 portionate numbers of skulls and sterna of Meionornis and 

 Euryapteryx respectively. Taking these as guides, I have 

 divided the leg-bones into somewhat similar proportions ; and 

 although, doubtless, some bones of crassa are included in 

 casuariniis, and seme of the latter in crassa, I do not think 

 that it affects the general results much, and it cannot invali- 

 date the conclusions arrived at as to the average dimensions 

 of the leg-bones in each species. 



