Systematic Position o/Zeledonia coronata. 15 



eyes on a first examination, nevertheless they are real. 

 They seem to indicate that Zeledonia should be regarded as 

 a primitive Thrush, in the wide sense of the word; but to 

 this point we shall return later. ' 



The tympanic cavity in Zeledonia is extremely shallow. 

 Bounded posteriorly by the conch-like tympanic wing- of the 

 exoccipital (PI. II. fig. 9, l.o.io.), it passes upwards into 

 the squamosal prominence to terminate some distance above 

 the squamosal head of the quadrate in the form of a low 

 hook-shaped ridge. The termination of this hook, which, it 

 must be remembered, is the termination of the free edge of 

 the tympanic cavity, lies behind and beneath the base of a 

 conical process of the alisphenoid. The articular surface for 

 the squamosal head of the quadrate, it should be observed, lies, 

 relatively, remote both from this alisphenoid process and the 

 termination of the free edge of the tympanic wing. Another 

 point of some importance to be noted here is the fact that, 

 after the removal of the tympanic membrane, the aperture 

 of the recessus tympanicus posterior will be found only after 

 a careful examination in the form of a minute foramen 

 which leads into a small chamber formed by the absorption 

 of the cancellated tissue around the semicircular canals, and 

 is strictly confined to this region. The aperture of the 

 recessus tympanicus anterior, though small, is quite normal 

 in position. 



Turning now to the palate, the chief point of interest will 

 be found in the maxillo-palatine processes, here reduced 

 to slender stylets of bone, the free ends of which are bent at 

 a sharp angle so as to lie parallel with the vomer and on 

 either side thereof (PL II. fig. 7, mx.p.). 



In the lateral view of the skull it will be noted that the 

 postorbital process is barely visible (PI. II. fig. 9, p.o.p.), 

 whilst the interorbital septum is much fenestrated, only a 

 very slender bar of bone remaining, which runs forwards 

 from the membranous orbito-sphenoids to join a small pillar- 

 like remnant of the septum that remains at the anterior 

 wall of the orbit. 



The anteorbital plates are large and have entirely replaced 



