Ac. 4.1 SIIUFELDT ON THE OSTEOLOGY OF .SPEOTYTO. 91 



the original division of this bony style into three separate bones, the 

 maxillary, malar, and squamosal, are here entirely effaced. As a whole, 

 it is compressed from side to side, and of ample size in comparison with 

 other bones of the head. At about the locality of the malozymotic 

 suture the bone throws upwards a thin expansion that meets the de- 

 scending i^ostfrontal, thus completing the orbital circumference at that 

 point. Its anterior and fixed extremity is made up by the maxillai-y, 

 Here it forms externally a portion of the posterior surface of the bill, 

 while internally it assists in forming the roof of the mouth and floor of 

 the nasal cavities, and otherwise behaves as already described. The 

 lachrymals are extrejuely spongy in texture, covered by an outside delicate, 

 compact bony casing. They articulate above by a ginglymoid joint with 

 the posterior border of the nasals, resting below on the spongy bones de- 

 veloped from the superior surfaces of the maxillaries. They are limited 

 to a slight movement inwards and outwards, and aid in separating the or- 

 bital cavities from the rhinal chamber. Externally they present for ex- 

 amination a shallow groove traversing the bone obliquely downwards and 

 forwards and a little inwards for the lachrymal duct. The orbital cavities 

 are very large, and remarkable for the completeness of their bony walls 

 and the near aj^proach their i)eripheries make to the circle, any diam- 

 eter of which measures the merest trifle above or below two centimetres. 

 The septum in the adult bird has rarely more than one small deficiency 

 of bone in it. This usually occurs in about the position shown in PI. I. 

 The sutures among the various bones have entirely disappeared, nothing 

 being left to define the exact outline of the vomer especially. The gToove 

 for the i)assage of the olfactory nerves forward is well marked, the cra- 

 nial foramina for them being distinct, one in each orbital cavity. This 

 also apiDlies to the openings for the optic nerves. The extent of the roof 

 is increased on either side by a superorbital process (shown in PI. II, 

 Fig. 1) that points downwards, backwards, and outwards, and serves for 

 membranous attachment. The posterior walls are marked by ramifying 

 grooves for vessels. They have a direct forward aspect, which is en- 

 hanced by the low descent of the broad and thin postfrontals. Ante- 

 riorly, the aperture between these and the rhinal vacuities is diminished 

 by the lachrymals externally and by a wing-like plate thrown ofl' from 

 the prefrontal internally. This latter bone here terminates in a sharp 

 concave border, with a descending ridge on either side just within it. 

 The floors of the orbits are more complete than is usually seen in the class, 

 due to the flatness and position held by the pterygoids and palatines, 

 the wmg-like process of the ethmoid just referred to, and the pterapo- 

 physial processes of the basi-sphenoid. The sclerotals number from 

 fifteen to sixteen, all of them being about the same length, but varying 

 as to their width ; in figure they are trapezoidal and universally oblong, 

 with the short parallel side in the circumference of the cornea and tlie 

 opposite one resting in the periphery of the posterior heniisi)here. We 

 have never observed one that was wide enough to ai)pear square. 



