CHECKLIST OF THE SNAKES OF MEXICO 6 



than those prescribed defeats the purpose of the rule and is contrary 

 to its statement and implication. The vacillation shown by several 

 herpetologists in its interpretation and use is rather surprising. 



The synonymy includes a reference to the original description of 

 the name used; references to original descriptions of all synonyms 

 having type localities in Mexico; a reference to one or more illustra- 

 tions of the species, if any are known to us ; a citation of the first ap- 

 pearance of the combination we use ; and references to any other works, 

 especially recent, that we consider particularly pertinent. For each 

 species, these references are arranged with all the different specific (or 

 subspecific) names in chronological order; however, different combina- 

 tions of one specific appellation follow the first citation of the name, 

 even though recently originated combinations miay be long ante- 

 dated by other (different) names applied to the same species. If sev- 

 eral references are included for a given combination, they are arranged 

 chronologically. If portions of a name in a synonymy are given in 

 brackets, this means that the name was not given in full in the article 

 cited, the bracketed portion being omitted; if other references follow 

 for that combination, it is not implied that in them the name is ab- 

 breviated. The statement of ranges is followed by a list of actual 

 localities from which the species is known, if there are relatively few ; 

 or, if the species is a common one, at least all states in Mexico from 

 which it is known are listed. Where localities are cited, confusion with 

 state names is obviated by citation of the latter in italics or by en- 

 closure of the locality names in parentheses or brackets. The generic 

 synonymies include all names, as far as we can determine, that have 

 as genotype a species occurring in Mexico or, in certain cases, nearby 

 areas. In the generic synonymies are cited any synoptic treatments 

 of recent date ; the nature of the synopses — whether monographic, re- 

 gional, or otherwise — is usually indicated. The arrangement of the 

 families and subfamilies is systematic, but the genera are listed alpha- 

 betically within these groups. The species of each genus are also listed 

 alphabetically. The genera are distinguished in one key, in which ap- 

 pear page references to the separate keys to species of individual 

 genera. Since the species are arranged in alphabetical order for each 

 genus, page references are not given in the species keys. 



The extraordinarily large number of forms listed (469) may lead 

 some authorities to think that we have recognized an unduly large 

 proportion of invalid names. We take recourse in the fact that we 

 are frequently merely stating an opinion, open to criticism and cor- 

 rection if facts so indicate. In general we tend to preserve names for 

 recognizable forms until there is adequate proof that they are vari- 

 ants, aberrations, or something else as the case may indicate. We pre- 

 fer to use specific names for populations not known to intergrade with 



