374 KANSAS UNIVERSITY SCIENCE BULLETIN. 



HETERODON Latreille. 



Heterodon Latreille, Hist. Nat. des Rept., IV, 1799, p. 32; Baird and Girard, 

 Cat. N. Amer. Rept., 1853, p. 51; Boulenger, Cat. Snakes Brit. Mus., II, 

 1894, p. 153. 



Posterior maxillary teeth much enlarged. Rostral plate very 

 high, with upturned edges and anterior face flat. A small 

 azygous plate behind the rostral. In two species there are sev- 

 eral other small plates near the azygous. Anal plate divided. 

 Caudal scutella in two series. Scales keeled, in 23-25 rows. 



The Spreading Vipers are commonly supposed to be very 

 poisonous. It is hard to understand how they received this 

 reputation, as they are harmless. It may be because of their 

 ugliness, or because they are often mistaken for Copperheads 

 and Copperheads mistaken for them. Scientists considered 

 them poisonous because the posterior maxillary teeth are much 

 enlarged. It is now known that they are not poisonous. 



KEY TO SPECIES. 



I. — ^No scales between prefrontals .H. platyrhinus. 



II. — Prefrontals separated by scales: 



1. — Scales in 25 rows. Prefrontals separated by scales H. simiis. 



2. — Scales in 23 rows. Prefrontals and internasals separated by scales. 



H. nasicus. 



Heterodon platyrhinus Latreille. 



Spreading Viper. 

 Coluber heterodon Daudin, Hist. Nat. Rept., VII, 1799, p. 153. 



Heterodon pUityrhinus Latreille, Hist. Nat. des Rept., IV, 1800, p. 32; Baird 

 and Girard, Cat. N. Amer. Rept., Pt. I, Serp., 1853, p. 51. 



Heterodon niger, H. cognatus, If. attnodcs, Baird and Girard, Cat. N. 

 Amer. Rept,, 1853, Pt. I, Serp., pp. 54, 55, and 57. 



Twenty-five rows of scales ; inferior row not keeled ; scales 

 rounded at the tips. Frontal wide anteriorly, narrowing rap- 

 idly toward the posterior end. Superciliaries very wide, 

 longer than the frontal. Occipitals pentagonal, short and nar- 

 row. Prefrontals of medium size, irregularly pentagonal. In- 

 ternasals triangular, with the apex pointing inward. Rostral 

 prominent, but not as large as in H. nasicus. Azygous plate 

 extending half-way between prefrontals. Rostral extending 

 half-way between internasals. Loreal short, much higher 

 than long. Oculars nine to eleven. Upper labials eight. 

 Lower labials generally eleven. Temporals 3-4 or 4-4. Gas- 

 trosteges 125-150. Urosteges 40-60. 



