158 OX LEPTOSOMA DISCOLOR. 



greater length of the trachea, are well ossified, and only separated by 

 narrow intervals. They gradually narrow as they approach the thorax, 

 the last two being the narrowest of all. The penultimate tracheal ring is 

 produced downwards in a triangular way behind, as is the terminal one 

 in front ; behind, this last ring bears the anteriorly directed narrow 

 pessulus, which intervenes behind between the inturned ends of the first 

 pair of bronchial semirings, but in front does not appear, stopping short 

 before it reaches the anterior surface of the bifurcating trachea. 



Like the tracheal rings, the first three bronchial semirings are well 

 ossified, and separated from each other only by very narrow interannular 

 intervals. They are nearly straight, with only a very slight concavity 

 upwards, and increase in depth as they descend. In front the semirings 

 P. Z. S. 1880, of opposite sides are separated from each other by a small notch ; behind 

 P* ' 4 they are less and less complete as they go downwards. The first semi- 



rings are posteriorly closely applied to, though separate from, the 

 pessulus, and are apparently continued on, as cartilaginous rings, 

 posteriorly, so as to form complete or nearly rings. The posterior ends 

 of the second and third semirings where they appear behind are widely 

 separated from their fellows of the other side. The fourth and succeeding 

 bronchial rings are all cartilaginous. Of these the fourth is the largest, 

 being nearly straight, and slightly more prominent than the others. To 

 its middle, rather towards its posterior margin, is attached the (single) 

 intrinsic syringeal muscle. The rings succeeding the fourth ring rapidly 

 become more and more complete, at the same time that the bronchus 

 becomes less capacious, the whole tube tapering away from this ring as it 

 approaches the lung. The fifth and sixth semirings are more slender 

 than those that succeed them, and are slightly concave upwards. The 

 remaining ones are straighter and deeper. Except between the fourth 

 and fifth, and fifth and sixth semirings, the interannular intervals are 

 exceedingly narrow. 



This syrinx does not show much similarity of form to that of Coracias 

 garrula, the only one of the family of Coraciidae that I have been able to 

 examine as regards this point. At the same time it does not much 

 resemble that of any Cuckoo I am acquainted with. 



Reviewing the facts already stated, it is clear that the affinities of 

 Leptosoma to the Cuculidae are very remote, whilst, on the contrary, its 

 relations to the Coraciidae are quite the reverse. The subjoined tabular 

 statement (p. 159) of the principal points in the structure of the three just 

 named groups will perhaps render this additionally clear. 



In common with both Cuculidae and Coraciidae, Leptosoma possesses a 

 nude oil-gland and long caeca, two carotids, and the f em oro- caudal, semi- 

 tendinosus, and accessory semitendinosus muscles. Wherever there is 

 any difference, Leptosoma resembles the Coraciidae ; and the same story 

 is told by the pterylosis and tensor-patagii arrangement. 



