MOEPHOLOGY OP THE OWLS. 



13 



The Maxlllo-jugal Arch. 



The maxilla is iudistinguishably fused with the premaxilla, aud is indeed entirely 

 covered by that bone externally. 



The maxlllo-pulatlne iwocesses in the Asionidse are of considerable size, highly pneu- 

 matic, being composed entirely of spongy tissue, and project backwards in the form of 

 large bullse, rising on each side above the quadrato-jugal bar so as partly to obliterate 

 the lachrymo-nasal fossa, which is reduced in some cases to the vanishing point, in \^^ 

 Gymnasio, for example, only a minute hole being left. This lateral and upward growth 

 of the process forms in Bubo, Gymnasio, and Ninox a quadrate mass at the infero- 

 posterior angle of the beak. In Asio, Scops, and Surnia this lateral mass is less 

 developed, and it is wanting altogether in other forms, such as Surnia and Speotyto, for 

 example, where the upward growth of the buUate process may be seen filling up the 

 lower portion of the lachrymo-nasal cavity. The lachrymal, it should be remarked, fits 

 very closely on the hinder end of this lateral maxillo-palatiue mass. Compared with the 

 maxillo-palatines of the Falconiformes, it is interesting to notice that the lachrymo-nasal 

 orifice of the antrum is incomplete above, inasmuch as the inner border of the dorsal 

 surface does not rise upwards to join the descending process of the nasal. The palatal 

 vacuity in the floor of the antrum, which lies in the triangle formed by the palatine, 

 premaxilla, and maxilla (PI. 1. fig. 8), is large, as in the Falconiformes, and this traced 

 forwards will be found to lead into the spacious anterior palatal vacuity. 



The maxillo-imlatine processes of Photoclilus differ from those of the remaining 

 Asionidae merely in their somewhat smaller size, their lateral extension beiug less. That 

 is to say, they do not extend outwards to fuse with the descending maxillary process of 

 the nasal. They may best be described perhaps as intermediate in character between 

 those of the Asionidse and Strigidse. 



In the Strigidse the maxillo-palatine processes are relatively much longer than in the 

 Bubonidse, and differ from them in shaj)e, forming delicate backwardly-directed and some- 

 what spindle-shaped processes. Viewed laterally, they are seen to lie near the middle 

 line and to leave a large cavity between themselves and the descending (maxillary) 

 process of the nasal. The lachrymo-nasal apertiu-e of the antrum is wanting altogether, 

 but the palatal aperture is large. 



The palate of the Owls aj)pears at first sight to be schizognathous ; in reality, however, 

 it is desmognathous, for although the Inillate portions of the maxillo-palatines are widely 

 separated in the middle line, the palate is nevertheless bridged by the ect-ethmoid 

 ossifications extending from the nasal septum outwards and downwards on either side 

 to join, posteriorly, the maxilla. 



The Vomer, Palatine, Pterygoid, and Quadrate. 



The vomer is short and blade-shaped, but generally more or less inflated in appearance, 



so much so, in Asio and StrLv, for example, as to become fusiform. In Asio it is pneumatic. 



In Surnia it is vestigial. In Speotyto, Xinox, and some other genera it appeal's to be wanting. 



It is supported by a pair of small spurs projecting inwards from the dorsal border of the 



