REPORT ON THE ANATOMY OF THE PETRELS. 



33 



last tracheal rings, forming together the framework of the lower larynx. In most cases 

 the last tracheal ring bears a well-marked antero-posterior pessular bar. 



It is in the genus Pelecanoides (figs. 3, 4) that the typical construction of the syrinx 



Fig. 3. — Syrinx of Pelecanoides urinatrix, from before. 1 



Fig. 4. — The same, from behind. 



of the Tubinares is seen in its simplest form ; it will, therefore, be described first on the 

 present occasion. 



The last tracheal ring is complete in front, and not modified in shape ; posteriorly it 

 is produced downwards into a well-developed pessulus, so forming a complete three-way 

 piece. The first bronchial semi-rings are united in front, where they are produced 

 triangularly downwards ; behind, their inturned ends do not unite either with each other 

 or with the pessulus, or with the second semi-rings. These last, as well as the third, 

 fourth, and fifth, on wdiich is inserted the muscle, are all similar in shape, and separate 

 from each other ; they are closely approximated in front, gradually getting shorter 

 posteriorly. 



Garrodia, which may be considered typical of the Oceanitidae, is anteriorly (fig. 5) 



Fig. 5. — Syrinx of Garrodia nereis, from before. 

 a. The last tracheal ring, from below, to show the pessular bar. 



Fig. 6. — The same, from behind. 



almost the same as Pelecanoides, but the first, second, and third bronchial rings are 

 complete (fig. 6). The last tracheal ring bears a complete pessulus (5, a). 



1 This and the succeeding figures of the syrinx of the Tubinares have been drawn as nearly as possible of one 

 uniform size, irrespective of that of the originals, and are also slightly diagramatic. The bronchial rings are numbered 

 from 1-5 ; the tracheal are marked 0, 00, 000, &c, in the reverse direction. 



(ZOOL. CHALL. EXP. PART XI. 1882.) L 5 



