The Amphibian larynx. 289 



which have acquired an attachment to it (compare P'ig. 34 with 

 Fig. 42). Suggestions of sexual dimorphism are shown here, the en- 

 tire laryngeal apparatus of the female being smaller than that of 

 the male. 



7. Hylidae. 



These forms constitute a natural group characterized by 1) an 

 excessive degree of sexual dimorphism ; the male larynx being several 

 times larger than that of female ; 2) abnormal size of the male larynx 

 in proportion to the body of the animal, and 3) a tendency to the 

 formation of nodules of cartilage in the tendons of the muscles and 

 in the vocal chords to act as sesamoids. The rotation of the carti- 

 lages noticed in Uana has here reached the extreme, involving the 

 annulus to such an extent that its plane almost coincides with the 

 frontal plane of the body, and lies closely applied to the concave 

 (cardiac) edges of the arytaenoids. The forms investigated in detail 

 are Hyla versicolor (Figs. 48—50), Acris gryllus (Fig. 51), Choro- 

 johilus feriarum (Figs. 52 — 55) , and Hylodes picker ingi (Figs. 56, 

 bl). The details of special interest are as follows and may be 

 seen by a comparison of the figures. The smallest species show in 

 the male the largest laryngeal apparatus proportionately as well as 

 the most striking disproportion in the sexes. In a male specimen of 

 Ghorophilus feriarum measuring but 29 mm from nose to posterior 

 end of body, the glottis slit in the fresh condition limited by mucous 

 folds measured 4 mm, or nearly one seventh the total length of the 

 body; while in a female of 33,5 mm total body length the glottis 

 slit scarcely measured 1 mm. This disparity is shown in Figs. 52 

 and 53, drawn to the same scale as shown by the hyoid skeleton. 

 The smallest species studied was Acris gryllus and here a male of 

 34 mm total length, possessed a glottis slit of 3 mm. The arytaenoids 

 are of similar shape in all the species examined, being in position 

 (i. e. amount of rotation) similar to those of Rana but more slender. 

 Their cardiac margin is more curved (Fig. 50, profile view) and they 

 lack the apical cartilages. The annulus is extremely slender and al- 

 most without processes; the only ones appearing are the bronchials. 

 These are in the form of very much reduced hooks, lifted far out of 

 position by the more complete rotation of the plane of the annulus 

 (Figs. 50 and 57). 



These processes in Acris are reduced to minute hooks and in 

 the females of Ghorophilus are entirely wanting. The entire annulus 



