THE LAEYNX IN SAXJEOPSIDA. 313 



All the Sauro23sida possess a larynx, a trachea, and one 

 or two kings. The bronchi do not divide dichotomously, as 

 they do in Mammalia. 



In Chelonia and Crocodilia the larynx consists of a 

 circular cartilage, apparently corresponding with both the 

 thyroid and the cricoid of the higher Vertehrata ; and of 

 the arytenoid cartilages, articulated with its anterior and 

 dorsal edge. 



The Lacei-tilia have, for the most part, a similar larynx, 

 but the circular cartilage is often interrupted by round, 

 or elongated, membi-anous f ontanelles. In the Chamseleons, 

 the mucous membrane of the larynx between the circular 

 cartilage and the first ring of the trachea protrudes in the 

 form of an air sac. 



In the Anvphisboenoidea, and in the Ophidia, the skeleton of 

 the larynx consists of two lateral longitudinal bands of carti- 

 lage, united by from foiir to sixteen transverse bauds. In 

 other words, the structure which answers to the circular 

 cartilage is greatly elongated, and has many transversely 

 elongated fontanelles. There is a single arytenoid car- 

 tilage, which is sometimes represented by a process of the 

 anterior dorsal margin of the circular cartilage. An 

 epiglottis is rarely present. 



In Birds there are distinct thyroid, cricoid, and arytenoid 

 cartilages, which may be more or less completely ossified. 

 Sometimes an epiglottis is added. 



The voice of Birds, however, is not formed in the larynx, 

 but in the syrinx, or lower larynx, which may be developed 

 in thi'ee positions : — 1. At the bottom of the trachea, from 

 the trachea alone. 2. At the junction of the trachea and 

 bronchi, and out of both. 3. In the bronchi alone. The 

 syi-inx may be altogether absent, as in the Ratitce and the 

 CathartidcB, or American vultures. 



The commonest form of syi-inx is the second mentioned 

 above, or the broncho-tracheal syrinx. It is to be met with 

 in all our common song birds, but is also completely deve- 

 loped in many birds, siich as the crows, which have no song. 

 In its commonest condition this form of syi-inx presents 



