Introduction 



Fig. 8. Bufo compactilis with vocal bladder extended 

 from base of throat. 



conspicuous in 

 Rana pipiens and 

 Rana sphenocepha- 

 la, Rana areolaia 

 and Rana cesopus 

 and in Rana virga- 

 tipes and Rana 

 grylio. (Fig. 9.) 

 Other Nortli 

 American mem- 

 bers of the Sali- 

 entia, as far as examined, have internal vocal sacs which show 

 their positions during the croaking but do not inflate so greatly 

 as to have the skin over them become thinned. 



Each species has its typical call, or " song," with definite 

 pitch and quality of tone. 

 The calls are exceedingly 

 simple, seldom involving 

 anything like rhythm or 

 melody. However, sev- 

 eral of the calls contain 

 notes of different pitch 

 usually sliding into one 

 another {Bujo jowleri, 

 Rana caieshiana), and 

 all are given with an em- 

 phasis and expression pe- 

 culiar to the given spe- 

 cies, so that we cannot 

 say that the calls lack 

 character. In a few 

 cases they are decidedly 

 musical and pleasing to 

 the ear. 



The typical call of 

 the Salientia consists of 

 a single note. The note 

 may be short and repeated in very rapid succession, as that of 

 Acris gryllus; or longer and given in less rapid succession, as is 

 that of Hyla pickeringii; or decidedly prolonged and given at 



Fig. 9. Leopard frog, drawn to show vocal 

 pouches extended at the shoulders. 



20 



