18/0.] ON THE ANATOMY OF CHAUNA DERBIANA. 189 



3. On the Anatomy of Chauna derbiana, and on the Systematic 

 Position of the Screamers (Palamedeidce) . By A. H. 

 Garrod, M.A., F.Z.S., Prosector to the Society. 



[Received January 5, 1876.] 

 (Plates XII.-XV.) 



In his memoir " on the systematic position of the Crested 

 Screamer (Palamedea chavuria)" published in the 'Proceedings' 

 of this Society*, Prof. Parker has placed that bird among the An- 

 seres, and away from the Rallidse, with which it had been generally 

 associated. In his "Classification of Birds "f, Prof. Huxley adopts 

 the same view as Prof. Parker. Both these distinguished authorities 

 base their opinions on anatomical considerations ; it therefore be- 

 hoves me to attempt to substantiate the different views expressed by 

 me in my paper " on certain muscles of Birds, and their value in 

 Classification "J, as it is so considerably at variance with that of the 

 authorities just mentioned. 



The great extent to which the skeleton is permeated with air 

 renders the features presented by the different bones of Chuna less 

 distinctive than in the majority of birds. For this reason the soft 

 parts will be first considered. 



Cutaneous System. Ptenjlosis. — Nitzsch has described the ptery- 

 losis of Palamedea cornuta and Chauna chuvaria ; and, as might be 

 expected, C. derbiana does not differ in any important particulars 

 from the latter. As he remarks, the most striking point observed in the 

 plucked bird is the extreme whiteness of the surface, which depends 

 on the fact that the skin is almost universally emphysematous to the 

 depth of nearly a quarter of an inch. On pressing with the finger, 

 the characteristic crackling of a tissue filled with air is most marked, 

 the only places in which it is absent, or nearly so, being the anterior 

 surfaces of the upper ends of the tibia, and, to a less degree, two 

 triangular spaces, equilateral, with their bases towards the middle 

 line, situated one on each side over that part of each pectoral region 

 which is near the head of the humerus, in the apex of the larger 

 triangular surface bounded by the superior and axillary margins of 

 the great pectoral muscle. 



In the Gannet and the Pelican the skin is likewise emphyse- 

 matous, but not exactly in the same way. In them the superficial 

 surface of the cutis forms a plane surface, and the deep layer 

 another, with the air-cells intervening between them, and the feather- 

 quills traversing them. In Chauna, however, these two cutaneous 

 layers are not definable, the whole presenting the appearance as if a 

 non-emphysematous skin had been forcibly blown up, so as to cause 

 its surface to be irregular and bubbled, more like an artificially 

 distended mammalian lung than any thing else. The feathers and 

 the semiplumes do not perforate the air-cells, but cause the skin to 

 be indented where they are situated. 



* P. Z. S. 1863. p. 51 1. t P. Z. S. 1867. p. 41"». } P. Z. S. 1874. p. 1 ] 7. 



