The first paper that could be regarded as revisionary in nature was "Remarks on the species of the genus Mustela" by the zoölogist and world-traveler, Charles L. Bonaparte, in Charlesworth's Magazine of Natural History, for 1838. In that paper three new names, _Mustela cicognanii_, _M. richardsonii_ and _M. longicauda_, all still valid, were proposed for American weasels. Audubon and Bachman in their "Quadrupeds of North America," which appeared in parts from 1845 to 1853, recognized 5 species. Actually they were dealing with only 3 taxonomically valid kinds. For one of these, _Mustela frenata noveboracensis_, they were misled by the difference in size between males and females, and in the males by the presence of a brown coat in some and a white coat in others. The male that was white in winter they regarded as _Putorius ermineus_ of the Old World; the male that was brown in winter they designated by their earlier proposed name _P. fuscus_, and the female they named _P. agilis_. The ermine, subspecies _M. erminea cicognanii_, they called _P. pusillus_. Their fifth name, _P. frenatus_, included at least some animals that today are assigned to the subspecies _M. frenata frenata_. Each of three and perhaps four of the five names employed by Audubon and Bachman embraced individuals of more than one species and in that sense the names were composite. Only five years later, in 1858, Professor Spencer Fullerton Baird's great work, "The Mammals of North America," made it clear that no American weasel was identical (in the modern subspecific sense) with any Old World weasel, and he applied most of his names in a correct zoölogical sense. It is true that he thought that the female weasel of the eastern United States was specifically different from the male, misapplied to it the name _richardsonii_, and did not correctly allocate every one of the few poor specimens available to him of the little ermine (_M. e. streatori_) of the Pacific Coast; but he did recognize that the least weasel was a distinct kind and his treatment in general was excellent. After Baird came a period of great confusion in which most writers did no better than had Audubon and Bachman, ordinarily confusing the two sexes as different species, and, in 1877 in his "Fur-bearing Animals," Elliot Coues went rather to the other extreme and allowed only 4 kinds to all of the Americas, regarding two of these, for purposes of zoölogical nomenclature, as identical with the European species.