98 [Senatk 



The particular eatures of this serpent will be given in the synopsis 

 of the New- York species. 



With the great increase in the number of known species of 

 North- American serpents, it has become impossible to place all 

 in the genera to which American herpetologists have hitherto 

 assigned them. The magnificent work of Dr. Holbrook, completed 

 in 1842, gives forty-seven species as the result of his laborious 

 investigations, continued for many years, among our Ophidia. 

 Owing, however, to the immense accessions supplied by the many 

 government expeditions, especially by the United States and 

 Mexican Boundary Survey, this number has been greatly enlarged ^ 

 so much so, indeed, that at least one hundred and thirty species. 

 are known to exist in this country, north of Mexico. The necessity 

 for greater precision in defining not only the specific, but also the 

 generic features of this vast number, induced Mr. Girard and 

 myself to take up the subject from the beginning, and remodel the 

 whole. In the course of our investigations, we discovered that many 

 genera, supposed to be common to Europe and America, had no such 

 extended distribution ; a critical comparison of different species 

 from the two countries, considered as of the same genus, resulting 

 in the detection of differences in generic features. 



It may be proper to premise that the diflQ.culties in the way of 

 any accurate comparisons or investigations into this subject were 

 greatly increased by the almost entire absence of systematic trea- 

 tises on the ColubridjE, to which family most North- American 

 species belong. The great work on Reptiles by Messrs. Dumeril 

 and BiBRON (Erpetologie Generale) has been delayed completion 

 for fourteen years, confessedly on account of the diflB.culty of 

 coming to any correct conclusion in regard to the classification of 

 the Ophidia. It is only within a few months that M. Dumeril has 

 presented his views of the arrangement of the serpents in a memoir 

 read before the Academy of Sciences, Paris, no copy of which has 

 yet reached this country. John Edward Gray, under whose au- 

 spices the valuable series of British Museum Catalogues has been 

 prepared, has likewise omitted the Colubridse. Other systematic 

 writers, as Fitzinger, Oppel, Wagler, &c. have, it is true, given 

 us something on this subject; but their arrangement has been 



