154 Transactions. — Zoology. 



ornithologists (or " procricoid " of Fiirbringer and other recent 

 writers). It is grooved on its dorsal or posterior face, and 

 laterally receives each of the posterior pieces of the thyroid 

 in a rounded notch. On its upper or anterior face it further 

 articulates with the pair of arytenoids. 



Each arytenoid is nearly Y-shaped, the stalk of the Y 

 being directed forwards and the fork backwards. "•' This 

 Y-shaped bone is, however, curved, so that the outer limb is 

 concentric with the margin of the thyroid, and the inner limb 

 (which is incompletely ossified) bounds the glottis. The pos- 

 terior end of the outer limb is sharply curved inwards to 

 articulate with the cricoid. 



I have described the larynx in some detail, as there appears 

 to be no easily available account of this organ in birds. 



The traclieal rings., which are incompletely ossified, overlap 

 one another alternately right and left. Each ring is narrow 

 in the median, dorsal, and ventral lines, but widens out 

 laterally. Any given ring overlaps its successor on one side 

 — e.g., right — but is overlapped by it on the other side — 

 e.g., the left, or vice versa. I noted a structure that appears 

 to be of some interest in connection with these tracheal rings 

 — namely, that on the dorsal median line a small nodule of 

 cartilage lies above the narrowed part of each ring; or, rather, 

 the nodules alternate with the rings at this point, but lie more 

 superficially. 



(c.) The Syrinx. 



The syrinx, or lower larynx, consists of seven closely 

 apposed rings, of which the fourth carries the pessulus, and 

 appears therefore to be the last tracheal ring (according to 

 Gadow, in Bronn's " Thierreichs : Aves ") ; consequently, the 

 syrinx is composed of four tracheal and three pairs of bron- 

 chial rings. 



The membrana-tympanica externa is supported by the last 

 syrinx ring and the three next bronehials. 



All the syringeal rings are separate, again indicating, pre- 

 sumably, the immature condition of the bird. 



The first syringeal ring (a) difi'ers but little from the 

 preceding tracheal rings ; it is, however, stouter. The next 

 ring (6) differs from the preceding ones in being incomplete 

 dorsally, where each end abuts upon a dorsal cartilaginous 



* Whether or not the anterior end articulates with the thyroid I was 

 unable to determine, as I did not wish to injure or displace the struc- 

 tures more than I could help. I have had to content myself with an 

 examination of one side of the structure only, so that if the bird passes 

 into the possession of a competent ornithologist he may be able to look 

 into such details as are of real importance. As I have no special know- 

 ledge of bird-anatomy from the point of view of the systematist, I have 

 purposely done as little damage to the structures as possible. 



