20 Mr. W. P. Pycraft on the 



more marked in Daulias luscinia (PI. II. fig. 4) and 

 Erithacus rubecula. 



Pratincola and Saxicola also belong to this type. So also, 

 it is significant to note, do Phylloscopus and Cisticola, and 

 probably the Warblers generally. 



The tympanic region of the skull in Zeledonia (PI. II. 

 fig. 9) is undoubtedly specialized in one respect, since the 

 jjrocessus zygomaticus squamosi has apparently been replaced 

 by a process of similar size furnished by the alisphenoid. 

 Pneumatic tissue is practically wanting. Indeed the peculiar 

 features of this region of the skull appear to have resulted 

 from a modification of the type of tympanic region in Sialia, 

 not as it is in adult life, but as it appears during its earlier 

 stages of development. 



As I have already remarked, the free edge of the lateral 

 occipital wing, which is relatively longer than in Menura, 

 terminates in a low ridge above the squamosal head of the 

 quadrate, leaving a notch between itself and what appears to 

 correspond to the zygomatic process, which, it is to be 

 especially noticed, is some distance from the squamosal arti- 

 culation of the quadrate. In this respect Zeledonia is quite 

 remarkable. In Cossypha and Geocichla the free edge of the 

 lateral occipital is continued upwards and forwards on to the 

 zygomatic process (PI. II. fig. 2, 1.o.w.) in the form of a strong 

 sharp ridge overhanging the bony ridge which formed the 

 external boundary of the meatus in Menura. From this the 

 passage to the more specialized form is easy. 



In Merula (PI. II. fig. 1, l.o.w.) the lateral occipital wing 

 passes upwards into what corresponds to the overhanging 

 ridge in Geocichla. But both the occipital wing and the 

 ridge continued therefrom are immensely developed, so as to 

 form a spacious chamber around the tympanic membrane. 

 Externally this chamber has the form of a bulla. The 

 incipient stages in the formation of this bulla are easily 

 traceable in Zeledonia. 



The skulls of Anthus and Motacilla, it should be re- 

 membered, resemble Sialia in the form of the tympanic 

 cavity. 



