72 CRITICAL NOTES. 
with any other species, and be either accompanied by one or more 
minor differences, or else the single difference must be so considerable in 
amount as to be capable of being accurately defined in words and easily 
recognised by the eye. 
The abundance and wide dispersion of individuals is not a very safe 
guide, for these may be affected by causes beyond our powers to recognise, 
or it may be impossible to ascertain which is the newly-developed form 
and which the old; so that if a new variety was gradually exterminating 
the older species, the parent might run the risk of being called a variety 
of its offspring. 
When, however, the distribution is taken in connection with rarity, 
it may sometimes help us to ascertain the true position of rare examples 
shewing a similar deviation from the commoner form, the constancy of 
which deviation cannot be readily ascertained. | 
The numbers before each species refer to those in the Catalogue of 
the Native Birds. 
12. Anthornis Auriocula. 
The type specimen of this species is in the Colonial Museum, and, after 
a careful examination, I can find nothing to distinguish it from A. melano- 
cephala. The second quill feather of the wing is acutely pointed, which 
proves that it is immature ; and, although the young of melanocephala 
has not yet been described, there is no reason to suppose that it would 
differ in any way from the present bird. Both are of the same size, and 
both come from the Chatham Islands, and the difference, if any, in the 
color of the iris cannot be taken as sufficient to establish a specific 
distinction, 
17. Xenicus Haastit. 
T have seen both the specimens of this bird on which Mr. Buller 
constituted his new species. They answer exactly to Pelzeln’s descrip- 
tion of his X. gilviventris, as quoted by Dr. Finsch (“Journal fiir 
Ornithologie,” July, 1870, p. 251). The black wing coverts, mentioned 
by Mr. Buller, are not characteristic, as they are found in all species of 
the genus, 
24. Gerygone Assimilis. 
Mr. Buller distinguishes this species from G. flaviventris by its 
slightly larger size, and a difference in the nest and eggs. Mr. Potts has, 
however, made a series of nests from one without a porch to one in 
