HuTTON. — On Moa-bonea at Kajjiia. 629 



The origin of this old lake is very obscure. There are no 

 extinct volcanoes in the neighbourhood, and there is no evi- 

 dence of the former existence of a glacier. An unequal move- 

 ment of the land appears to be the most probable cause ; but, 

 be this~as it may, it is evident that it was only during a por- 

 tion of the lake's history that the bodies of moas were floated 

 into it and buried iu mud. It is possible, but not probable, 

 that no nioas lived near the lake before that period, bat cer- 

 tainly they lived there afterwards, although none were buried 

 in the lake. Consequently we must suppose that different 

 climatic conditions prevailed during the time the moa-deposit 

 was formed from that which followed, and, probably, from that 

 which preceded it also. The burying of the moas was, most 

 probably, due to floods, caused either by heavy rain or by the 

 rapid melting of snow ; and if trees were also washed into the 

 lake they must have floated to a greater distance than the 

 moas — perhaps out of the lake altogether. The peaty layer 

 above the bones seems to show that the diluvial epoch was 

 followed by a specially dry epoch, which allowed vegetable 

 growth to accumulate on the bottom of the lake ; and the dry 

 epoch w^as succeeded by the present one. Evidently the bone- 

 deposit is an old one. 



Specific Characters in the Dinornithid^. 



Whenever we find an anatomical structure tolerably con- 

 stant in the moas we nearly always find it exhibited by 

 bones of very different sizes— so different, indeed, that we 

 cannot suppose the two birds to which the bones belonged to 

 have stood in the relation to each other of parent and off- 

 spring. If, therefore, the term " species" can be defined as a 

 group of individuals which resemble each other as much as 

 parents resemble their offspring it is evident that we have 

 two or more species belonging to the same genus, and that 

 the peculiar anatomical structure is of generic value. When, 

 however, we come to look for other characters except size to 

 distinguish between the species we generally find that the 

 subordinate anatomical characters are so variable that they 

 cannot be relied on for specific diagnosis, and we have there- 

 fore to fall back upon measurements of the bones. In fact, 

 structural characters, when not of generic importance, are 

 merely individual variations which are not transmitted. But 

 there is often in each series a complete set of connecting links 

 between the largest and the smallest bones, so that we feel 

 doubtful wdiere to draw the dividing-line. In my former paper 

 on the moas of New Zealand" I took individual skeletons, or 

 parts of skeletons, as guides for arranging the other bones into 



* Trans. N.Z. Inst., vol. xxiv., p. 93. 



