MOEPHOLOGT OF THE OWLS. 11 



Bubo, it is perforated near its superior border, so as to place the hinder division of the 

 olfactory cavity in communication with its fellow, at least in the dried skull. In Strix 

 the perforation, by its extension backwards, is converted into a deep notch. It is 

 interesting to note that owing to the ect-ethmoidal ossifications above described, the 

 nasal septum is not visible from the A'entral aspect of the palate, as ia the schizognathous 

 palates of certain Ealconiformes. That is to say, in the middle of the anterior palatal 

 A^acuity of the schizognathous Falconiform palate the nasal septu.m is plainly visible, 

 the roof of the cavity being formed l)y the premaxilla ; whilst in the Strigine palate the 

 roof of this cavity is formed almost entirely by the ossified ali-ethmoids, only the extreme 

 anterior end of this A'aulted chamber being formed by the premaxilla. 



The lachrymal differs conspicuously from that of the Falconiformes, and agrees closely 

 with that of the Caprimulgi. As in the last-mentioned group, there is no supraorbital 

 process, and the descending limb, which extends downwards to the quadrato-j ugal bar, is 

 greatly inflated by spongy tissue, and is attached to the under surface of the fronto-nasal 

 region of the skull, instead of the external border thereof as in the Falconiformes. It 

 varies somewhat in form in the different genera, but typically, in the Asionidae, it may 

 be described as columnar, and marked by a deep groove on its external face, near its upper 

 third, the groove passing forward into the lachrymo-nasal fossa. The latter, by the way, 

 is extremely small, having been practically obliterated by the great development of the 

 maxillo-palatine processes, which rise upwards to cover almost the entire anterior border 

 of the lachrvmal. In Bubo it is almost crescentic. the horns of the crescent beina: 

 directed outwards. In some species of Scops it is very small, tapering from above 

 downwards. In Syrnium, Surnia, and Asio it is perhaps most nearly columnar, and in 

 the two latter the lachrymo-nasal groove is especially deep. 



The lachrymal is largest in Strix, where it is subconical in form, with the apex pointing 

 forwards into the lachrvmo-nasal fossa, and the base hollowed to accommodate the eve. 

 It is grooved across the middle of its outer surface, deeply in some, slightly in others, 

 according to the species. Again, in some S2:»ecies, the lachrymal extends so far 

 forwards as to leave only a small hole representing the lachrymo-nasal fossa, whilst in 

 others, e. g. S. poensis, a comparatively large fossa is left, which is open below down to 

 the quadrato-j ugal bar. These differences in the form of the lachrymal, it should be 

 noted, are correlated with others in other parts of the skull. 



The Cranial Cavity. — The met encephalic fossa in the Asionidse very closely resembles 

 that of the Falconiformes, being both moderately wide and fairly deep. The cagus 

 foramen lies very near the exoccipital border. The internal auditory meatus is deep, 

 and separated from the vagus foramen by a swollen ridge. About midway along the 

 anterior lateral border of the fossa, mesiad of the mouth of the trigeminal foramen, lies 

 the small abducent foramen. The oculo-motor lies behind and below the optic foramen 

 on a level with the external angle of the sella turcica. 



In the Strigidte the vagus foramen is reniform, and the internal auditory meatus is in 

 a very shallow pit into which the foramina for the facial and auditory nerves open. The 

 foramen for the oculo-motor is minute, and lies on the extreme external angle of 

 the sella turcica between the optic and trigeminal foramina : passing through the wall. 



2* 



