614 Mr. W. P. Pycraft on the 



the skull from the outer margin of the forameu magnum. 

 The lateral oecipital ring is continued outwards and forwards 

 beyond the tympanic membrane, so as to form a scroll-shaped 

 niche or pocket. The uppermost border of this flange does 

 not extend above the level of the tympanic rim. Imme- 

 diately above this flange, and separated therefrom by a notch, 

 is a low ridge running forwards for a short distance. In 

 Synallaxis orbignii, for example, this notch-divided ridge is 

 continuous with the flange. 



After the removal of the tympanic membrane this cavity 

 will be found to be extremely shallow, leading upwards and 

 backwards, with a mass of diploid tissue in which a small 

 and posterior tympanic recess can be traced — the rudiments 

 apparently of the larger recess usually found in birds. The 

 anterior tympanic recess which opens into the floor of the 

 antero-ventral moiety of the cavity is somewhat more deve- 

 loprd. The superior recess is apparently wanting in the 

 Passerine skull. 



A "squamosal prominence" is not distinguishable in this 

 skull ; and there is but the merest apology for a processus 

 zygomaticus sqnamosi ; this process is separated from the 

 termination of the free end of the rim of the tympanic 

 cavity only by a small, barely perceptible notch. 



The otie and squamosal heads of the quadrate are placed 

 close together. 



The orbit is moderately large, and but little protected 

 from above, the interorbital region of the frontal being 

 deeply cut away. The interorbital septum is membranous, 

 but strengthened by a bony bar extending in the form of a 

 slender curved rod backwards from the middle of the free 

 hinder border of the mesethmoid, and terminating just above 

 the optic foramen. 



The lachrymal is wanting ; I searched carefully in two 

 separate skulls for evidence of this bone and found none. 

 The lachrymo-nasal fossa is greatly reduced. 



The mesethmoid is extremely small, and is partly filled 

 up by the large and inflated antorbital plate. The nostrils 

 are of the schizorhinal type (p. 619). 



