142 



CHAPTERS ON THE NATURAL HISTORY 



n-t allied by the posterior swelling of the end of the tail, forming 

 now the first loose joint of the rattle. This process is repeated 

 on succeeding exuviations the new joints being always larger 

 than the old ones, as long as the snake grows. Perfect rattles, 

 therefore, taper toward the point, but generally the oldest (ter- 

 minal) joints wear away in time and are lost. As rattlesnakes 

 shed their skins more than once every year, the number of joints 

 of the rattle does not indicate the age of the animal, but the num- 

 ber of exuviations which it has undergone." 



Another interesting structure is found in our common Bull or 

 Pine snake (Pityopliis sayi bellona). Years ago, when I was as- 

 sisting in the work of the Keptile Department of the Smithsonian 

 Institution, Dr. Charles A. White, the distinguished paleontolo- 

 gist, came to me one day and asked if I had ever examined the 



FIG. 37. FLOOR OF THE MOUTH OF A BULL SNAKE (P. ,s. Mlona). 



Seen directly from above (reduced), a, Sheath of Tongue ; />, Epiglottis ; <-, Glottis. 



peculiar structure of the epiglottis in the Bull snake, and how 

 that by forcibly blowing and the consequent violent vibration of 

 the epiglottis, the snake could produce the threatening noise 

 that it did. Replying in the negative, I further remarked that. 

 the fact had not ever been published that I was aware. Shortly 

 after, Dr. White gave an excellent description of the mouth parts 

 of one of those snakes, and it was published in Tin- American 

 XtttiiruUst for January, 1884 (p. 19). My own figures illustrated 

 the paper, and these are here reproduced in Figs. .'57 and MS, and 

 will show how the vertical plate of the movable epiglottis />, 

 standing directly in the middle line and in front of the glottis c, 

 would vibrate whenever the breath was driven out of the aper- 

 ture of the latter. 



