370 



PROF. A. H. GARROD ON THE 



[Apr. 1, 



cord, which it resembles in consistence. The " mucous " tissue in 

 this case is entirely developed between the external fibrous covering 

 of the windpipe and the middle ring-carrying layer, the rings them- 

 selves not varying in the least, as far as I can detect, from their 

 arrangement in the female. 



Tetrao urogallus (a male, not quite full-sized, and without any 

 trace of the cervical loop developed) differs from the female of T. 

 tetrix only in a few details. All the rings and semirings are thinner, 

 and the interannular intervals greater. The posterior vertical bar is 

 undistinguishable. Anteriorly, however, the lowermost seven tracheal 

 rings are not thinned in the middle line, where they, above the pe- 

 nultimate, articulate above and below to form what becomes almost 

 an anterior vertical bar as well. The corresponding parts of the 



Fig. 20. 



Fig. 21. 



Front view. 



Tetrao urogallus. 



Back view. 



penultimate and last rings, considerably narrower than in T. tetrix, 

 expand and consolidate into an elongate lozenge, with a much shorter 

 one above it, from the lateral angles of which the rings are continued, 

 and from the inferior augle of the lower of which the articulating 

 (and subsequently fusing) surfaces for the anterior ends of the first 

 bronchial rings arise. The second semiring also articulates with the 

 first, as in the allied birds, with, however, a considerably larger inter- 

 annular interval than in T. tetrix. The lateral parts of the first 

 semiring being markedly convex upwards, at the same time that the 

 incurved last tracheal ring sends downwards rather lengthy processes 

 from its posterior extremities as well as the deep lozenge- shaped car- 

 tilage in front, the interval between the two agrees with the section 

 of a plano-concave lens. Some of the bronchial semirings are bifid 

 at their extremities ; and the bronchidesmus is very strong. 



Tetrao cupido is intermediate iu its tracheal bifurcation between La- 

 ffopus scoticus together with L. inutus, on the one hand, and Tetrao 



