1882.] ON THE ANATOMif OF FASSERINK BIROS. 569 



tares iu its dorsal wall, aud give off branches to the outer face of 

 the lung, representing the ectobroncliial system of birds. The ori- 

 fices with which the surfaces of all these canals, except the anterior 

 half of the mesobrouchium, are thickly set, lead into depressions, 

 which are often so deep as to become cylindrical passages, simulating 

 the parabronchia of birds. 



Thus, notwithstanding all the points of difference, there is a 

 fundamental resemblance between the respiratory organs of Birds 

 and those of Crocodiles, pointing to some common form (doubtless 

 exemplified by some of the extinct Dinosauria), of which both are 

 modiiications. 



3. Contributions to the Auatouiy of Passeiiue Birds. — Part 

 VI. ^ On Xeuicus and Acanthisitta as types of a new 

 Family {Xenicidee) of Mesomyodian Passeres from New 

 Zealand. By W. A. Forbes, B.A., Fellow of St. John's 

 College, Cambridge, Prosector to the Society. 



[Received June 19, 1882.] 



A few months ago I received, through the kindness of my friend 

 Prof. Jeffrey Parker, of the University of Otago, New Zealand, a 

 small collection of birds in spirit from that country, which included 

 most of the peculiar forms of Passeres found there. Amongst them 

 were single specimens of Xenicus longipes and Accmthisitta chloris, 

 the examination of which has proved to be of especial interest. 



The genus Xenicus was founded by the late Mr. G. R. Gray - for 

 the reception of the Motacilla longipes of Gmelin *, Lafresnaye 

 having some twenty years previously established Acanthisitta for 

 Sparrman's Sitta chloris *. 



Subsequent ornithological writers have pretty unanimously assigned 

 both these forms to the " Certhiidse " or their immediate neigh- 

 bourhood, iu company with Sitta, Sittella, and their allies. The 

 peculiar structure of the tarsus in Xenicus first induced me to 

 examine these birds more closely, with the unexpected result that I 

 find that the two genera in question are true Mesomyodian forms, and 

 therefore iu no intimate degree related to such Oscines as those just 

 mentioned. 



The subjoined drawings of the syrinx of Xenicus — with which in 

 all points Acanthisitta appears to agree in every essential respect — 

 will show that it has none of the complex nature of that organ in 

 the Oscines, the thin lateral tracheal muscle terminating on the 

 upper edge of a somewhat osseous box formed by the consolidation 

 of the last few tracheal rings, and there being no other intrinsic 



' For Part V. vide antea, p. 544. ^ Eev. Mag. Zool. 1842, Ois. pi. xxv 



- Ibis, 1862, p. 218. * Mus. Carls, fasc. 2, no. 33. 



38* 



