384 MR. w. A. FORBES ON THE [May 4, 



where it is well developed, the last ring being here notched above. 

 Behind, the ultimate and penultimate rings are united by a vertically 

 disposed median bar. The last ring forms a three-way piece, there 

 being a forwardly-directed narrow pessulus developed from its hinder 

 margin below. The pessulus is apparently membranous, in this spe- 

 cimen at least, except at its base. The first bronchial semirings are 

 still narrower than the last tracheal one and strongly arched, being 

 concave downwards. They are separated by a very slight interval 

 indeed from the last tracheal ring (three-way piece), and are nearly in 

 contact with each other iu front in the middle line ; behind they are 

 inturned and somewhat thickened. To the middle of each ring, or 

 a little posteriorly to this point, is attached the lateral tracheal muscle. 



Fig. 2. 



Syrinx of Eurylcemus ochromclas, X 5, viewed from iu front. 

 p, the " pseudo-ring." 



which is extremely slender and hardly visible when dry. The second 

 bronchial semirings are shorter than either the first or third ; they 

 are slightly deeper than the first pair, but are narrowed behind. 

 Being only slightly concave downwards, a considerable membrane- 

 covered fenestra is left between them and the first pair. AVhat at 

 first looks like a bronchial semiring is interposed between what are 

 here described as the first and second of that category. This 

 pseudo-ring is most evident in front {vide fig. 2), but is also visible 

 when dry behind ; it is apparently due to the accumulation of tissue 

 inside, forming the outer boundary of each glottis. The third and 

 fourth rings are slightly concave upwards : they are deeper, especially 

 behind, thinning away towards the front, than those that preceded 

 them. The fifth and other succeeding rings are typical, unmodified 

 bronchial rings, which more and more encroach upon the memb7-ana 

 tympaniformis, and eventually almost overlap behind. The second 

 and succeeding semirings are more or less incompletely ossified at 

 their ends. 



In Cymhirhynchus macrorhynchus (figs. 3-5), the syrinx is 

 constructed on essentially the same plan, with some modifica- 

 tions. The trachea, below the insertion of the extrinsic muscles 

 (on the last ring but six), appears to be somewhat laterally com- 

 pressed and diminished in size. In the specimen before me the 

 last few tracheal rings are somewhat irregular iu their disposition, 



