Birds of New Zealand. 215 



so many intermediate forms, that even the supposed line of 

 division between both sexes is exceedingly difficult to draw. 

 Moreover (and this is peculiar to Dinarnis maximus) there are 

 scarcely two skeletons entirely alike ; there are some which 

 have a remarkably long metatai-sus, whilst the other leg-bones 

 do not (at least at the same rate) increase in size ; others are 

 much stouter for their height. Altogether we might trace 

 the same peculiarity in size and form as in a series of human 

 skeletons selected at random. 



The same is the case wdth the skeletons of the immature 

 birds of this species, of which we possess portions from the 

 chick to the full-grown giant bird, where the tarsal epiphysis 

 is not yet so closely united with the metatarsus, that the line 

 of junction is still visible, where also a similar variety of form 

 can be traced. 



The difference in size between Dinornis maocimus and Di- 

 nornis robustus, the next in size, is very marked and constant. 

 Of the latter we obtained a series of two sizes, of which the 

 largest might be assigned to the female. 



Between Dinornis robustus, ingens, gracilis, and struthioides , 

 besides their well-defined specific characters, there are also 

 distinct breaks, each species possessing at the same time two 

 constant sizes. 



Of Meionornis casuarinus a series of four clearly defined 

 sizes are in our possession ; so that we might conclude that 

 we have two closely allied species before us, of which the two 

 largest sizes represent male and female of the one, and the 

 two smaller male and female of the other. 



A considerable difference in size occurs between the smallest 

 species of Meionornis casuarinus and the largest species of 

 Meionornis didiformis. In the latter we can distinguish also 

 four sizes, with a gradation similar to that observed in the 

 former ; so that I am led to believe that this species, like Mei^ 

 onornis casuarinus, consists of two subspecies. 



If we compare two skeletons of Apteryx australis, male and 

 female, and two of Apteryx owenii, male and female, with 

 each other, a similar distinct gradation is observable. 



Palapteryx elephantopus has also four well distinguishable 



