DEVELOPMENT OF THE SKULL IN THE OSTRICH TEIBE. l%1 



ethmoid. The alse of the septum, or roots of the great inferior turbinal cartilages, are 

 ossified continuously in the same way, and as a roof to the continuous vertical plate ; 

 but the mass of these cartilaginous folds continues soft in the adult. Seen from within, 

 the "upper," "middle," "inferior," and alinasal turbinals form one connected, conti- 

 nuous series of swelling masses (Plate VIII. fig. 7) ; but the representative of the upper 

 turbinal and its cribriform plate in the Mammal is here a mere descending wing 

 (Plate X. fig. 1, al.e.), only folding upon itself where it passes insensibly into the roots 

 of the inferior turbinal ; and the olfactory lobe lies between it and the middle plate 

 (Plate X. fig. 1, i), in that chink which is so copiously bridged over, and thus converted 

 into a vertical row of holes in the Mammal. The spaces seen on the side of the upper 

 turbinal fold behind (Plate VIII. fig. 1, p.e.), where it passes into the " pars plana," are 

 not for olfactory filaments, but depend upon a certain unfinished condition of the carti- 

 laginous lamella, and are quite inside, and even behind that part of the olfactory crus 

 which gives ofi" the filaments. A fissure lower down (Plate VIII. fig. 1, al.e.pp.) partly 

 divides the upper turbinal lamella from the large but very simple "pars plana," but 

 above that there is a broad continuous connecting plate. Below, at its external angle, 

 the pars plana is connected with the outstanding, foot-shaped, lower end of the inferior 

 turbinal (Plate X. fig. 1, a.i.t.) by a narrow isthmus; so that there are three antorbital 

 plates, or rather regions — an upper or inner, a middle or lower, and an outer and 

 somewhat anterior lobe ; these belong respectively to the upper, middle, and lower 

 turbinals. 



The only fold or outgrowth which can safely be said to belong to the middle turbinal 

 is near the base of the pars plana (Plate VIII. fig. 11, m.t.h.) ; it is triangular, horizontal, 

 and runs outwards and forwards, lying between the largest posterior part of the inferior 

 turbinal and the proximal plate of the prevomer. The most complex part of the inferior 

 turbinal (Plate X. fig. 3, i.t.) is the fullest or hinder part; and although much less 

 complex than that of the Cassowary, or even than that of the Emu, it is yet greatly in 

 advance of the same part in the Bhea, the Tinamou, or the typical bird. The septal ala 

 (Plate X. fig. 3, al.s.) passes outwards, downwards, and then inwards, walling in the whole 

 nasal labyrinth, save for the chink between the free edge of the alse and the base of the 

 septum (Plate X. fig. 3). Where the aliseptal cartilage begins to turn downwards it 

 sends off" an outgrowth, which is directly vertical behind, and afterwards turns inwards; 

 at this anterior part it splits into two lamellae, which curl upwards, each being about a 

 semicircle (Plate X. fig. 3, i.t.). But posteriorly these secondary lamellae are divided 

 again ; and of these tertiary folds, the nearest but one to the septum forms more than a 

 complete coil (Plate X. fig. 3, i.t.). Below these lamellae another has been given off 

 from the outer (primary) wall (Plate X. figs. 3, 4, 5, n.t.), and when this reaches the 

 ahnasal region it becomes as complex as the front part of the inferior turbinal ; this is 

 the " alinasal turbinal." The septum, as soon as we pass in front of the olfactory bulbs, 

 is very thick at top ; it then becomes thin, and thickens into a strong (trabecular) beam ; 

 this beam being underlaid by the " rostrum," and this again by the vomer (Plate X. 



