Systematic Position of Zeledonia coronata. 21 



The three great air-sinuses of the cranium are not very 

 largely developed in any of the Passeres. 



The recessus tympanicus anterior appears to be invariably 

 present and well defined ; but in the small Turdiform skulls — 

 e. g. Sialia, Pratincola — the superior and posterior recesses 

 are ill-defined, passing insensibly into the general diploid 

 tissue of the skull. 



In Zeledonia this diploid tissue is extremely reduced and 

 the superior tympanic recess is Avanting. The posterior is 

 present, however, but is very small ; it opens external^ by 

 a small foramen above the fenestral recess. Only among 

 Laniine skulls have I noticed a similar lack of diploid 

 tissue. But even there some vestiges of the superior recess 

 are to be found. These are present in the form of a number 

 of small foramina arranged in a semicircle, leading from the 

 articular surface for the squamosal head of the cpiadrate 

 backwards and downwards to the top of the fenestral recess. 



In the larger Thrushes, e. g. Merula, the superior and 

 posterior recesses are moderately large. The aperture of the 

 former lies between the squamosal and the articular surfaces 

 of the quadrate, while the entrance to the latter is through a 

 cribriform plate above the fenestral recess. 



The Palate. — That the form of the pterygo-palatine arti- 

 culation in Zeledonia is more primitive than that which 

 obtains in Sialia or Erithacus for example, there can be 

 little doubt. In support of this view I would cite the con- 

 ditions which obtain in Menura. In this bird the hemiptery- 

 goid element does not fuse with the palatine till late in life 

 (PI. II. fig. 10, h.pt.), but when this has taken place the 

 appearance of the palatine is precisely the same as that of 

 Zeledonia. 



The nature of the palato-pterygoid articulation in Menura, 

 and the transformation in the details of this articulation 

 which can be traced in Zeledonia, Erithacus, Sialia, and 

 Turdus for example, on the one hand, and the peculiar 

 modifications which obtain in forms like Bucco and Mega- 

 lama for example, on the other, seem to shew conclusively 

 that the fusion between the pterygoid and the palatine, which 



