Royal Microscojncal Society. 47 



and squamosals (ep., sq.) are seen all surmounted by the squared 

 parietals (p.). The peculiarly ornithic condition of the great 

 sphenoidal wings is best seen in a skull which has had the whole 

 face cut away through the orbits (Plate VI., Fig. 2, al. s.). They 

 are placed far more from without inwards than longitudinally, and 

 are attached to the orbital plate of the frontal (o.f.). A subvertical 

 view of the post-orbital plane (Plate VI., Fig. 2) helps much to the 

 understanding of this very complex and most instructive skull. The 

 narrow, superorbital plates of the frontals (/.) are cut through, and 

 these large orbital plates (o.f.) are seen from their scooped front 

 aspect. They are sending bony spiculas into the up-tilted cranial 

 floor towards the " anterior sphenoid," which lies in the middle. 

 The upper plate of each frontal is grooved for the "olfactory 

 nerve " (1). Propping up these plates, another bony bar is seen ; 

 this is an azygous " ectosteal " orbito-sphenoid ; it has three points 

 below, and rests upon the prse-sphenoid and the narrowest foremost 

 part of the " orbito-sphenoidal " cartilaginous alae, which are here 

 unusually large for a bird; these together are pyriform, and on 

 each side there is a largish " endosteal " orbito-sphenoid ; they are 

 unequal. Between them there is a large vertical plate of endosteal 

 bone (Plate V., Fig. 1, and Plate VI., Fig. 2, p. s.) ; this is the 

 " prae-sphenoid "; it lies above and in front of the opotic foramen (2). 

 An irregular " fenestra," or rather " fontanelle," of the unhardened 

 membranous cranium extends upwards on each side between the 

 orbito-sphenoids mesially and the orbital plates of the frontals 

 and " ali-sphenoids " laterally. The large squamosals are scarcely 

 seen in this view (Plate V., Fig. 1, sq.) ; but in the lateral view 

 they show nearly all their relationships. The large cartilaginous 

 wings of the posterior sphenoid (" al. s") had a fenestra in their 

 centre ; here the bone is still very thin, and I suppose, as in most 

 birds, the upper and lower regions were separately ossified. A very 

 small additional centre is seen on the near margin of each bone. 

 Between the lower edge of the " ali-sphenoid " and the upper edge 

 of the huge complex " basi-sphenoid " there is a suture, and in this 

 suture two holes; the outer, or posterior, is the "foramen ovale" 

 and the inner the " foramen rotundum." 



The sectional view of the median part below is the "prse- 

 pituitary " part of the basi-sphenoid cut through close to the " basi- 

 pterygoid processes." Seen in a shadowy manner, at a distance, we 

 have, below, the occipital condyle at the mid-line (o. c.) on each 

 side, and in front of that the swellings caused by the cochleas where 

 the underlapping " basi-temporal " ankyloses with the basi-occipital 

 (b. t.). The outermost swellings are the " basi-temporal floors " of 

 the tympanic cavity. The two " anvils " that look towards each other 

 are the " quadrate bones." They must be considered soon. 



The huge " internal ears " only come fairly into view at two 



e 2 



