The Amphibian larynx. 293 



number of cartilagiuous elements lying along the sides of the trachea 

 and often grotesquely shaped. 



4. Among the Urodeles, the arytaenoids are the most constant 

 while the tracheal elements vary with the relative length of the 

 trachea. 



5. In a few Salamandrids, all the respiratory cartilages have 

 been lost by a secondary reduction, and the animals, having passed 

 the gill period, respire by means of the integumental and pharyngeal 

 capillaries. 



6. The short and wide trachea of the Anura necessitates the 

 formation of a cartilaginous ring, the annulus, which is formed by 

 the fusion across the median line of the anterior portions of the 

 tracheal elements. The posterior tracheal pieces generally persist as 

 the bronchial processes. 



7. The annulus produces several processes, of which the most 

 constant are the posterior pharyngeal, which lies in the median 

 line; the anterior pharyngeals, for the attachment of muscles; 

 and the cardiac, which often become closely attached to the ary- 

 taenoids. 



8. The Anuran arytaenoids are generally huge concave organs, 

 which by their shape greatly increase the resonance of the voice. In 

 Rana a pair of tiny cartilages, the apical cartilages, segment off 

 from the main mass. 



9. In the more specialized Anura the primitive relations of the 

 larynx are confused by its rotation about a transverse axis. 



10. Characteristic of the Hylidae is the formation of sesamoid 

 cartilages which facilitate the action of the muscles and reinforce 

 the vibration of the vocal chords. 



11. In Bombinator and in the Aglossa the voice is increased bj 

 the formation of a resonance box, formed either by the annulus alone 

 [Bombinator) or by the annulus and parts of the hyoid apparatus 

 together. 



This resonance box may become partly or almost wholly ossified 

 and attain a proportionately enormous size. In Pipa the arytaenoids 

 are ossified and greatly developed, while in Bactylethra they are 

 much reduced. 



20* 



