1899,] INTEHNAL ANATOMY OF NOTORNIS. 93 



as does the ovary, the immaturity of the bird. The so-called 

 " thyroid " (which, according to Gadow, is the " cricoid " of recent 

 authorities) is a nearly flat, somewhat spoou-shaped, plate (a), 

 slightly convex ventrally, espHoially posteriorly ; it is feebly pointed 

 in front and truncated behind. The posterior half of its lateral 

 margin is slightly upcurved and forms a cartilaginous ridge, 

 with which is articulated a second bony plate (h), which is 

 separated from (a) by a narrow cartilaginous area. The posterior 

 piece (b) belongs apparently to the "thyroid," with which it 

 becomes continuous, according to Tiedemann and Dumeril, 

 in very old birds. The piece h curves sharply inwards dorsally, 

 and articulates with the side of a small median bone (fZ), the " cri- 

 coid " (or " pro-cricoid " of Eiirbringer) ; it is hexagonal in shape, 

 with the anterior side largest and a groove along the middle ; its 

 lateral edge articulates with the incurved margin of the plate b, 

 while its antero-Iateral angle of each side supports the hinder end 

 ot the " arytenoid " (c). 



The arytenoid is again imperfectly ossified, as is indicated in the 

 figure ; it is a Y-shaped bone, with the middle limb directed for\^'ards, 

 and it appears to be here connected with the epiglottis, but of this 

 I am uncertain. I only cleaned the left side of the larynx, as of the 

 syrinx, as I did not wish to do more injury than was necessary. 



The main part, and stronger half, of the bone articulates with the 

 " cricoid," while the feebler, and at present cartilaginous, limb (c) 

 of the Y supports the margin of the glottis and ends freely behind. 



As to the musculature of the larynx, I am unable to say any- 

 thing, as I did not think any important point would be presented 

 by its arrangement. 



The rings of the trachea are only partially ossified ; they overlap 

 one another alternately right and left (fig. 4), and are, of course, 

 narrower in the middle line dorsally and ventrally. Overlying this 

 region, on the dorsal line, is a small nodule of cartilage (x). 



(d) The Syrinx (figs. 4-6, pp. 94, 9-5, 96) consists of seven closely- 

 apposed rings {a-g), of which the fourth (rf) carries the pessulus, so 

 that I presume, from Gadow's account of the structure in general, 

 this ring should be regarded as the last tracheal. If this be the 

 case, then four of the syringeal i-ings are tracheal and three are 

 bronchial. 



The " membrana tympaniforinis externa " is supported by the 

 last syringeal ring {g) and by the three following bronchial rings 



(I, li, HI). 



The rings of the syrinx {a-g) are in the present specimen 

 separate, owing no doubt to the growth of the bird. 



As the arrangement of these rings is unlike anything figured by 

 Gadow in " Bronn," I will describe the syrinx in some detail. 



The ring a differs little from the preceding normal tracheal 

 ring (1), which, indeed, ovei^laps it on the right side. The next 

 ring (6) is, however, incomplete dorsally, where its end is enlarged 

 and abuts upon a cartilaginous plate, in the centre of which is a 

 small nodule of bone {y). 



