58 
As to the systematic position of this form, much doubt and uncertainty existed till the appearance 
of a paper “On the Structure of the genus Orthonyx ,” by the late Mr. Forbes, the Prosector to the 
Zoological Society, in which he gave the results of a careful dissection and comparison of the typical 
Orthonyx spinicauda of Australia with the so-called Orthonyx oohrocephala from New Zealand * This 
examination convinced him that the two forms are not really congeneric, the New-Zealand bird, 
apart from its entirely dissimilar coloration, differing from the Australian in its more slender bill, 
less development of the nasal operculum, less spiny tail, and more slender claws. He states further 
that internally the skull and the syrinx exhibit differences, slight in amount, but greater than those 
usually found in birds of the same genus ; and he concludes thus : “ Under these circumstances it 
seems that Clitonyx of lieichenbach f will be the correct generic term for the New-Zealand birds, as 
Lesson’s name Mohoua, though of prior application, is not only barbarous but, what is more 
important, liable to be confounded with Mohoa , also a genus of Passeres from the Pacific Subregion. 
In the present unsatisfactory condition of the systematic grouping of the Oscinine 1 asseres, it is 
impossible for me to point out clearly any definite position either for Orthonyx or Clitonyx , though 
both forms might, I apprehend, be safely placed in Mr. Sharpe s somewhat vaguely defined 
‘ Timeliidte.’ ” 
The above conclusions were based upon an examination of C. ochrocephala only fiom New 
Zealand. It will be seen that I have placed the North-Island form (C. albicapilla) in the same 
genus. I am aware that Dr. Finsch has proposed to separate these birds generically, and that his 
views have been adopted by one or two of our local naturalists. It appears to me, houerei, quite 
impossible to find any sufficient distinguishing characters. It will be seen, on comparison, that the 
wing-feathers present the same proportional arrangement in both species, and that the bill and feet 
of C. albicapilla, although somewhat more slender, are formed on exactly the same model as in 
C. ochrocephala. Apart from these external characters, the two forms agree in other essential 
respects. The peculiar feature of a black mouth (in the male) is common to both ; their style of 
song is the same; the sexes are alike in both, and their habits of nidification are very similar. 
It is true that the colour of the plumage is different, and that there is some dissimilarity in the 
coloration of the eggs, but these differences have no generic value. On these grounds I adhere 
to my old contention | that the two species belong to the same genus. 
Dr. Gadow, in the ‘Catalogue of the British Museum’ ( l . c.), while accepting this relationship 
of the two forms to each other, has grouped them together with the New-Zealand Creeper in the 
genus Certhiparus. So far, however, from adopting this arrangement, I have deemed it necessary 
not only to separate these birds generically but to place them in different Families. 
* “ Both forms are typical Singing-birds (‘ Oscines Normales ’), with a well-developed Oscinine syrinx with its normal 
complement of four pairs of muscles. Of these the short anterior muscle runs to the anterior end of the third bronchial semi- 
ring alone in 0. spinicauda ; whilst in 0. ochrocephala this ring receives its muscular supply from a fasciculus of the long anterior 
muscle. They thus differ essentially from Menura, with which they have been associated, that bird having but three pairs of 
muscles peculiarly arranged. In this, as in all other points examined— with one exception in the case of Orthonyx spinicauda— 
these birds quite resemble the normal Passeres, as they do in having the bilaminate tarsus and reduced ‘ first’ (tenth) primary 
nearly always associated with the normal Acromyodian syrinx. Orthonyx spinicauda, however, has a peculiarity quite unknown 
to me in any other bird, inasmuch as its carotid artery, the left alone of these vessels (as in all Passeres) being developed, is not 
contained anywhere in the subvertebral canal, but runs up superficially in company with the left vagus nerve to near the head, 
where it bifurcates in the usual manner In Orthonyx ochrocephala the left carotid retains its normal situation, though 
the point of entrance into the canal is somewhat higher up than is usual in other Passeres. (1 . Z. S. 1882, pp. 544, 545.) 
f Handb. Spec. Ornith. p. 167 (1851). 
t Trans. N.-Z. Inst. vol. vii. p. 204. 
