6 BULLETIN 18 7, UNITED STATES NATIONAL MUSEUM 



semipopular works, in which the nomenclature is often extremely 

 faulty), in order to determine the proper taxonomy for any group of 

 animals ; it is quite certain that no means could be found to define the 

 kind of works it would be necessary and desirable to consider, and 

 those which (for this purpose) could be ignored. A further result 

 would be the sanction of activities of the professional "name-giver," 

 for, as pointed out in the Bulletin of Zoological Nomenclature (part 3, 

 p. 25), it is quite out of the question for a body of zoologists sitting 

 as an International Conmiission to pass judgment upon the professional 

 conduct of a particular zoologist, and upon that decision to reject or 

 accept his work. Were it possible to render decisions upon these two 

 points — quality of publications and qualification of author — perma- 

 nent suppression of secondary homonyms would be a desirable rule, 

 but under existing circumstances it seems entirely impractical. 



The present interpretation of the "homonym rule" requires a few 

 changes in current nomenclature and affects the names of nine forms 

 in this checklist: Arizona elegans elegcms^ A. e. occidentalism Dry- 

 marchon coi'ais melanums^ Elaphe subocularis^ Manolepis putnafmi, 

 Masticophis tdeniatus omatus^ M. f-ageUwrn lineatus, Rhadinaea 

 vittata, and AgTcUtrodon hilineatus. Were secondary homonyms 

 suppressed permanently these forms would be known as follows, re- 

 spectively: Arizona arizonae arizonae^ Arizona arizonae occidentalis, 

 Dryinarchon corais melanocercus, Elaphe sclerotica^ Manolepis nasu- 

 tus^ Masticophis tacniatus girardi^ M. fagellmn striolutus, Rhadinaea 

 fulmvittis, and Aghistrodon (no name). 



ZOOGEOGRAPHICAL DISCUSSION 



The occurrence of such a large number of forms in Mexico may be 

 explained by the extremely rugged and divergent topography of the 

 country, reflected not only in a diverse snake fauna but in an equally 

 remarkable aggregation of species in many, if not all, other groups 

 of plants and animals. That Mexico is situated on the border between 

 temperate and tropical zones, rather than completely in either of them, 

 is equally as significant as its topography. Likewise, because of its 

 position, Mexico has acted as a very important f aunal paleopeninsula, 

 and to a lesser extent as a f aunal neopeninsula ; actively throughout 

 most of Tertiary and to a lesser extent in relatively recent times it 

 has been a cul-de-sac for southward-migrating species.^ In view of 

 these facts it is not too surprising that Mexico has, probably, a richer 

 fauna than any other area of the globe of equal size. However, observ- 

 ing the very considerable increase during the past few years in number 

 of forms known from the country, we can guess that still many more 



» Schmidt, Karl P. Corollary and commentary for climate and evolution, Amer. Midi. 

 Nat., vol. 30, 1943, pp. 241-253. 



