MOEPUOLOGT OF THE OWLS. 15 



backward and downward position of this, and in its greater separation from the squamosal 

 head. Furthermore, the pneumatic apertures in the Striges do not extend below the 

 base of the otic head, whilst in the Palconiformes they extend downwards to the base of 

 the orbital process. In the AsiouidiB the pneumatic apertures are two in number, and 

 open, one on either side of the base of the otic head, into a deep groove. In the Strigidse 

 there is but a single aperture ; this is large and opens beneath the otic head. 



The form of the quadrate in Sfr/'d^ is markedly different from that of any of the 

 Asionidse, the orbital process being reduced to a short spine, seated rather below 

 the middle of the body of the quadrate, which is bent sharply backwards forming 

 a Y-shaped angle with the process in question. Furthermore, the internal mandibular 

 condyle in the Strigidse is comparatively feebly developed, whilst in the Asionidae it is 

 nearly as large as the external condyle, and in Bubo, for example, projects downwards 

 far below the articulation of the hinder end of the pterygoid. 



The squamosal head of the quadrate is bounded in front by a zygomatic process, 

 which is longest in Asio, and especially so in A. madaguscarlensis, in Avhich the 

 maximum length appears to be reached, and behind by the i^rocessus articularls 

 squamosL This last often extends downwards and inwards to join the pretemporal wing 

 of the basitemporai. 



The Mandible. 



The most conspicuous feature of the mandible in the Asionidse and Protodilidge is the 

 wide angle formed by the rami, and the great length of the internal angular process. 

 The angular is sharply truncated. A ramal vacuity is generally present. Tiie only 

 suture that can be cut is the dentary, and this is often obliterated. The coronoid ends 

 in a free point partly closing the ramal vacuity. 



In the Strigidse the angle of the rami is less open ; the coronoid is less degenerate 

 than in the Asionidse, but has fused more completely with the jaw, reducing the size 

 of the lateral vacuity. 



The Hijoid. 



The hyoid resembles that of the Accipitres among the Falconiformes. The basihyal 

 is triangulcir in form, deeply notched in front, and has the posterior angle drawn out 

 into a small pair of cerato-hyals. The basibranchial is more or less rod-shaped and 

 produced backwards between the cerato-branchials. The cerato-branchials are long and 

 slender, and surmounted by a pair of slender, ossifled epi-branchials. 



III. The Skull of the Nestling. 



The sutures of the skull appear to remain distinct, at least until the young is nearly 

 half-grown. The changes which take place between the skull of the nestling and that 

 of the adult are at once striking and instriictive. 



It is to be regretted that the Museum Collection contains no nestling skulls of the 

 Strigidae. The following description is based on skulls of Syrnium aliico and Speotyto 

 cunicularia. 



