34 



THE VOYAGE OF H.M.S. CHALLENGER. 



A very similar type of syrinx prevails in the other Oceanitidse, and is also that found 

 in the genera Procellaria (figs. 7, 8), Cymochorea (figs. 9, 10), and Halocyptena. In all 

 these the first few bronchial rings closely resemble in character tracheal rings, being nearly 

 straight, closely apposed to each other, and more or less ossified. Anteriorly they may be 

 united with one or more of the preceding tracheal rings, and very frequently the first two, 

 or three are quite complete here in the middle line. There is always a well-developed 



Fig. 7. — Syrinx of Procellaria pclagica, from before. 



Fig. 8. — The same, from behind. 



and complete pessular bar, supported behind by the last tracheal ring. "With this bar 

 one or more (sometimes three or four) of the bronchial rings may fuse by their coalesced 

 ends posteriorly, forming a broad three-way piece ; or these rings may be complete rings 

 closely apposed, though apparently not anchylosed, to each other in the pessular bar. 

 Different specimens vary slightly in the exact number and disposition of these bronchial 

 rings, and sometimes are not exactly similar on the two sides. 



Fig. 9. — Syrinx of Cymochorea leucorrlioa, from before. 



Fig. 10. — The same from behind. 



In Prion vittatus (figs. 11, 12), the first bronchial ring is either small or fused with 

 the second, which is anteriorly entire : this is not the case with the three succeeding 

 ones. The last three tracheal, and first two — or on one side three — bronchial rings 

 form a pessular box, continuous anteriorly with the inturned anterior ends of the third 

 semi-rings. The fourth pair takes no share in the formation of the box. In Prion 

 desolatus there is only one complete bronchial ring, which may be the first, or the first 



