LARYNX OF REPTILES. 529 



inner surface of the cricothyroid. In Lacerta and Ascalabotes 

 the corresponding fold is very narrow, and the chirping call-note 

 of the Gecko may depend rather on the vibration of the margins 

 of the glottis than on the vocal folds, which cannot be brought 

 into contact or be made tense. In the Chameleon, the lining 

 membrane of the larynx is produced between the cricothyroid and 

 first tracheal ring into a pouch. In the Stellio of the Levant the 

 tracheal rings are osseous : in most Lizards they are cartilaginous. 

 The trachea is remarkable for its width in Platydactylus yuttatus, 

 but the diameter is reduced to one half in Platydactylus vittatus. 

 In the Chameleon and most other Lacertians it is still narrower. 

 Amongst the Chelonia the Hawksbill Turtle ( Chelone imbricata) 

 shows a glottis undefended by retroverted papilla?, or by an epi- 

 glottis, but capable of being accurately closed by its constrictors. 

 The thyroid cartilage in all Chelonia is distinct from the cricoid : 

 the arytenoids are triangular, and their inner facet is large in 

 Emijs and Testudo. The ordinary sound produced by the larynx 

 of the Chelonia is a sort of hiss. The European fresh-water Tor- 

 toise emits a low piping note, and Agassiz records the same fact in 

 regard to some North American Emy dians. * In Chelone my das the 

 f rima glottidis ' supports on each side a mucous fold, which serves 

 to produce a low grunt or bark at certain seasons. In some Tor- 

 toises ( Testudo tabulata, T. elephantopus) a triangular membrane 

 ascends from the base of the larynx to the ( rima,' dividing it into 

 two parts. The rings of the trachea are entire and cartilaginous : 

 in some species the trachea bifurcates half way towards the 

 lungs, the bronchi being of great length, and one of them usually 

 describing a large curve : in Testudo gr&ca the left bronchus is 

 three fourths longer than the tracheal trunk ; but in Testudo 

 coue'i the trachea is one fourth longer than the bronchi. The 



o 



production of the snout in the Trionycidce enables the terminal 

 nostrils to be raised above the surface of the water, to respire, 

 without exposure of the animal. 



In the Nilotic Crocodile the mucous membrane is produced into 

 a fold on each side the ( rima glottidis : ' the folds deepen as they 

 extend backward, and are produced into a pair of pointed pro- 

 cesses above the arytenoids* The broad cartilaginous plate of 

 the basihyal rises in front of the glottis like an epiglottis. On 

 divaricating the rimal folds they are seen to bound a wide pouch 

 anterior to and above the true ( aditus larynstis,' which is much 



/ o 



shorter than the ( rima,' The thyroid and cricoid coalesce to form 

 one annular cartilage supporting the pair of arytenoids. The 



1 CCC. vol. i. p. 284, 

 VOL. I. Bl M 



