SEKPEXTS OF NORTHEASTEKX UNITED STATES 



361 



Venomous and nonvenomous snakes 



Of the species occurring within the area here discussed, only 

 three are venomous. These are the banded, or northern rattlesnake 

 (p. 3ST) ; the massasauga, or prairie rattlesnake (p. 386) ; and the 

 copperhead (p. 385). The three venomous species are closely 

 related, all belonging to the family of Crotalidae, or pit-vipers, 

 marked by the presence of erectile poison fangs on the upper jaw 

 and by the presence of a deep pit between the eye and the nostril. 

 The head is more or less markedly triangular in outline, and sepa- 

 rated from the body by a relatively constricted neck. The rattles 

 of the two species of rattlesnakes are of course an unmistakable 

 characteristic. The copperhead bears no such distinguishing mark, 

 and is frequently confused with the harmless hog-nosed snake, or 

 blowing adder (p. 368), the water snake (p. 377) and occasionally even 

 with the familiar milk snake (p. 374). A careful reading of the 

 descriptions and inspection of the cuts given of these species, and 

 comparison with those of the copperhead will make the points of 

 difference clear. 



Much attention has naturally been paid to the Crotalidae by 

 American authors, and numerous papers on the subject have been 

 published. By far the most valuable and comprehensive work on 

 the venomous snakes of North America is that by Dr Leonhard 

 Stejneger ('95), curator of reptiles and batrachians at the United 

 States national museum, to which the reader is referred for a very 

 detailed discussion of our poisonous snakes. 



Fig. 1 Illustrating nomenclature of the head scales of serpents 



Nomenclature of the scales 



Certain terms frequently used in describing the characters of the 

 species require definition here. 



The vertical or frontal plate (v) is the central, shield-shaped plate 



