1899.] ISTEBNAL ATSTATOMY OF NOTORICIS. 93 



as does the ovary, tbe 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 couvex ventrally, espe.eially posteriorly ; it is feebly pointed 

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

 margin is slightly upcurved and forms a cartilaginous I'idge, 

 with which is articulated a second bony plate (6), which is 

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

 piece (6) belongs apparently to the " thyroid," with which it 

 becomes continuous, according to Tiedemann and Dumei-il, 

 in very old birds. The piece b curves sharply inwards dorsallj', 

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

 coid " (or " pro-cricoid " of Flirbringer) ; 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-lateral angle of each side supports the hinder end 

 of 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 foi'wards, 

 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 ti-eely behind. 



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

 thing, as I did not think any important point \^ould 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 liue 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 (d) 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 rings are tracheal and three are 

 bronchial. 



The " membrana tympaniformis externa " is sitpported by the 

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



(I, li, III). 



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, overlaps 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 (?/). 



