HuTTON. — On the Moas of Netv Zealand. 101 



The species are not distinguished by any anatomical differ- 

 ences in the leg-bones, but merely by size. In many cases, 

 especially in the genera Syornis and EuryajJteryx, there are 

 considerable differences in the amount of divergence of the 

 metatarsal condyles, which may be of specific value, but I am 

 inclined to think that it depends largely on the age of the 

 individual. Also, the tibiae vary much in the curvature of the 

 shaft ; but there are complete gradations from one form into 

 the other, and I cannot think this curvature to be of specific 

 value. "-•■ 



There appear to be specific differences other than size in 

 the crania ; but this must be left for future investigation. So 

 far as the leg-bones are concerned, my examination has shown 

 that several of the species pass gradually one into another, so 

 that any line separating them must be an arbitrary one; and 

 I should not be surprised if further knowledge showed that this 

 applies to those species which at present appear to be distinctly 

 marked off. For we are here dealing with a large number of 

 individuals which lived for a very long time without the check 

 of natural selection to eliminate the iiitermediate forms — a 

 case which is probably unique in natural history. 



In the tables of measurements of each species I have given 

 first the measurement of Professor Owen's type, then those of 

 individual leg-bones found together, and then the maximum 

 and minimum size and robustness which I allow to each 

 species — the latter being represented by the girth at the 

 middle of the shaft. It may be thought that the twenty- 

 six species which I have admitted are too many ; but after 

 a careful consideration of the subject I have come to the 

 conclusion that a less number would not represent the 

 facts sufficiently, and would not give an adequate idea of 

 the great variety of form which the moas exhibit. In the 

 genus Syornis only the smaller individuals are found in the 

 North Island, and this gives us a maximum limit for S. casu- 

 arinus. The larger individuals of the genus, which are found 

 only in the South Island, show too great a diversity to be 

 included in one species at all uniform with S. casuarinus, 

 and consequently they must be divided into two. From this 

 we get an idea of the amount of variation to be allowed to 

 each species in the genera Euryajyteryx and Cela. With 

 Dinornis and Palapteryx the case is different, because with 

 them we have to take geographical distribution into considera- 

 tion, and smaller morphological distinctions may with advan- 

 tage be taken to differentiate species when they are combined 

 witli a different geographical distribution. It is also a question 

 which must be left for future investigation whether those 



* Trans. N.Z, Inst., vol. vii., p. 277. 



