866 



REPORT OF NATIONAL MUSEUM, 1898. 



expiration of the air contained in their volnminous lung. This sound, 

 althougli it can not be called a voice, is sufficiently loud to be alarming, 

 and serves, no doubt, as a defense. 



The question as to the number of species included in this genus is a 

 difficult one to decide. The P. melanoleucns may be always distin- 

 guished by color characters from the forms found west of the Mississippi 

 Eiver. From some of these it also differs in the shape of the head and 

 muzzle, but the most eastern of the western forms, P. sayi sayi, resem- 

 bles it in these respects. The Lower Californian form may be distiu- 

 guished from the P. melanoleucns by color characters and by the shape 

 of the head and muzzle, but between it and the P. sayi of the western 

 Mississippi region there is a complete transition in most of the charac- 

 ters. The California form resembles that of Lower California in form, 



Fig. 202. 



PiTYOPHIS SAYI BELLONA BAIRD AND GlEAED. 



= 1. 



a, sheath of tongue ; h, epiglottis ; c, glottis. 



From Dr. R. W. Shufeldt. 



but differs in color, while the Arizona form is in every respect interme- 

 diate between the Pacific form (P. catenifer) and the P. sayi of the 

 plains. These forms are tolerably constant and can be generally recog- 

 nized. The form of the rostral plate is the most characteristic pecul- 

 iarity, but from the nature of the case transitions occur. Under the 

 circumstances, I have adopted four species, of which the P. sayi has 

 two subspecies, one of which, P. s. hellona, is intermediate between its 

 typical form and the P. catenifer, the latter differing, however, in the 

 greater smoothness of the scales. 



SYNOPSIS OI*" SPECIES. 



Scales with stronger keels begiuuing on the fourth row ; head short, elevated ; ros- 

 tral plate compressed and narrowed above; no head stripes; dorsal spots few, 

 27-33 ou body P. mslanoleucus. 



Scales first keeled oti the sixth row; rostral plate narrowed above; head stripes 

 present ; spots numerous, 40-65 on body -P. sayi. 



