368 PROF. A. H. GARROD ON THE [Apr. 1, 



teriorly they are not expanded and scarcely touch ; anteriorly they 

 expand a little and articulate freely. The interannular intervals in 

 essential points are not different from the preceding genus. The 

 bronchial semirings below the second are peculiarly lengthy ; their 

 extremities turn inwards toward one another, and so slightly intrude 

 into the membranous inner wall of each bronchus. One or more of the 

 semirings may be bifid at their anterior ends. The bronchidesmus 

 is particularly powerful in the Tetraonidae, including Lagopus, and, 

 as it were, pulls the two tubes into nearer relationship than would 

 otherwise appear to be their tendency. 



Lagopus mutus agrees with L. scoticus in every respect. 



Tetrao urogallus and T. tetrix conform to a type which has several 

 important differences from Lagopus scoticus, although in common 

 they have the yielding cartilaginous (and never ossified) rings 

 throughout the organ under consideration, as well as the great de- 

 velopment in length of the bronchial semirings beyond the second. 



In the female of Tetrao tetrix the first feature that strikes the 

 observer is the consolidation of all the intrathoracic tracheal rings 

 along the mid-posterior surface into a vertical bar, rendered more 

 than it would be otherwise conspicuous by the considerable thinning 

 of the lateral third or more of each ring on each side, and the 

 consequent formation of lateral interannular spaces slightly deeper 

 than the rings enclosing them. In the adult bird no trace of the 

 transverse lines of junction between the constituent transverse 

 annular elements of this vertical posterior bar can be seen ; in the 

 young bird, however, they are conspicuous. Anteriorly the rings above 

 the antepenultimate are separated by an interval which slightly re- 

 duces the lowest of them, and that only, towards the middle line. 

 There is a median semifusion in front, of considerable breadth, be- 

 tween the antepenultimate and penultimate rings, below which a 

 broad cordiform cartilage represents the fused mid-anterior elements 

 of the penultimate and last rings, with which the anterior extremity 

 of the first bronchial ring is blended, and the second articulates, in 

 such a way as to form lateral extensions of its apex. The line con- 

 stituting the actual angle between the contiguous sides of the bronchi 

 — produced, as just indicated, by the apex of the cordiform cartilage, 

 together with the inferior margins of the lateral expansions, com- 

 posed of the anterior ends of the first and second bronchial semirings 

 — is less concave downwards than in Lagopus (in fact almost straight), 

 and much less so than in the other Gallinse. It has, in Tetrao, a 

 very slight descending protrusion in the actual centre — the apex 

 of the cordiform cartilage. Posteriorly each free end of the last 

 tracheal ring expands and sends downwards and outwards a small 

 process for the articulation and fusion with the similarly enlarged 

 extremity of the first bronchial semiring. Upwards it blends with 

 the base of the vertical posterior cartilage, which is considerably 

 broader opposite the lowermost three tracheal rings than higher up. 

 Into the middle of its base the narrow pessulus is seen to run. There 

 is a great similarity between the depth and shape of all the interan- 

 nular intervals in the bifurcating portion of the tube, the compara- 



