20 ME. W. P. PYCRAPT OJS^ THE 



anterior end of the mesethmoid plate. The palatal processes are vestigial, the 

 maxillary processes relatively large. 



The maxilla extends backwards, from the level of the maxillary process of the nasal 

 to the level of the tip of the orbital process of the quadrate, in the form of a long 

 slender rod constituting the outer sheath of the quadrato-jugal bar, and forwards as far 

 as the level of the anterior angle of the anterior nares. Its maxillo-palatine process 

 is very large and swollen, so much so as nearly to obliterate the lachrymo-nasal fossa. 

 The antrum of Highmore opens far forwards on its floor, and leads forwards by an 

 extremely short channel into a vault in the j)remaxilla roofed by ossified alinasals. 



The jugal has the usual elongated and splint-like form, and overlaps the quadrato- 

 jugal posteriorly and the maxilla anteriorly. 



The quadrato-jugal is long, extending forwards along the inside of the bar to beyond 

 the middle of it. 



The 2)ara sphenoid appears to present the usual elements — a basitemporal plate, a pair 

 of pretemj)orals, or alisphenoidal wings, and a rostrum. It seems to me a point of 

 some significance that the basitemporal plate is quite separate from the rostrum in 

 the youngest skulls in the Museum Collection, a sharply defined suture-line being visible 

 when the skull is seen in section. It suggests, however improbable it may seem on 

 reflection, that what appears to be the middle region of the parasphenoidal rostrum may 

 really be the floor of the basisphenoid ; the parasphenoid in this case would be 

 represented only by the basitemporal plate and the tip which projects beyond the 

 basisphenoid in such a way as to look as if it had been thrust through the antero -ventral 

 angle of that bone. So much of the bone as would underlie the basisphenoid is thus 

 supposed to have become absorbed. Elsewhere (p. 17) I have interpreted the features 

 observable in this region by supposing the basisphenoid floor to have become absorbed 

 and the parasphenoidal rostrum to be persistent. The reverse may be the case, though 

 it must be admitted the weight of probability is in favour of the earlier interpretation. 

 Instances of the replacement of one bone by another by absorption, till the invading 

 bone more or less completely establishes itself, are not unknown in the skull. The 

 stages in the process may be studied in the casque of the Cassowary, and in the growth 

 of the squamosal for example : both these elements were originally quite external, but 

 are now slowly working their way inwards so as to take part in the formation of the 

 cranial cavity. The point in question can only be determined by a careful examination 

 of much younger skulls than we at present possess. The remarkable shortness of the 

 rostrum in the Owls is a feature already commented upon. 



The vomer is small, and quite divorced from the hemipterygoid segment of the 

 pterygoid. Its support has now been transferred to the palatines, which send inwards, 

 for this purpose, from their mesial edges a pair of quadrate spurs. 



The lialatine may be described as scimitar-shaped, increasing in breadth gradually 

 from before backwards. It terminates anteriorly near the tip of the beak in a fine 

 point, but the posterior extremity presents some features of interest. Viewed from the 

 ventral surface, it will be seen that the movement towards the middle line has caused 

 the articulation with the pterygoid, which takes place at about this time, to form on the 



