HETERODON NIGER. 107 



by Catesby; later naturalists having only copied his description, or his plate, which 

 is one of the best in his work. Daudin and others speak of a black variety of 

 Heterodon, which has reference no doubt to this animal. I cannot, however, 

 consider it as a variety of any Heterodon, but as a distinct and separate species. 

 It cannot be a variety of the Heterodon simus, because the plates of the head are 

 so entirely different; oesides it is a much larger animal. It bears rather more 

 resemblance to the Heterodon platirhinos; from which it differs, however, con- 

 siderably, in the number of its abdominal plates and in its colour, which is so 

 constant that it must be taken as an essential character in distinguishing the 

 species. It differs furthermore from the Heterodon platirhinos in its habits, 

 preferring dry places; while the platirhinos selects rocky, shady, and damp situa- 

 tions. Finally, there would seem to be a difference of geographical distribution; 

 at least in some parts of the United States. Thus, in Carolina the Heterodon 

 platirhinos is common in the upper districts of the state, and I have never heard 

 of the black viper being found there; while the reverse is true of the sea board: 

 here the Heterodon niger is very common — the Heterodon platirhinos seldom 

 found. 



