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Show 458 DR. E. A. GOELDI ON THE [June 5, the subgenus Didelphys-D. marsupialis-with two varieties : D. marsupialis typica, very widely spread over the American continent and including even D. virginiana and D. ccdifornica of other zoologists, with a range extending to Chili and Brazil; D. marsupialis var. azarce, on the other hand, being confined to the countries bordering the Amazonian Basin, but ranging on the eastern coast to South Brazil. The characters are purely external and may be briefly referred to as follows :-Face without, or with indistinctly defined, black and white markings-var. typica; face with sharply defined black and white markings-var. azarce. In the list given of the specimens contained at that date in the collection of the British Museum from Brazilian localities I find four of var. typica (3 from " Brazil," 1 from " Eio de Janeiro") and two of var. azarce (both from Taquara, Eio Grande do Sul, collected by m y friend and colleague Dr. II. von Ihering). Well, according to the exposition of M r . Oldfield Thomas, there is absolutely no doubt that I should have to determine m y specimens from the Serra dos Orgaos as belonging to D. marsupialis var. typica. To anybody who has occupied himself seriously with the study of Marsupials, it is evident that the family Didelphyidse in general, and the genus Didelphys in particular, is, even in our days, what is called a " crux zoologica." On this point Mr. Oldfield Thomas says :-" With the exception of the short-tailed Opossums the series available for examination in the European museums seems to be fairly complete, but in the case of these more specimens are urgently needed before the species can be at all satisfactorily worked out and the present arrangement of that, the most difficult, group must be looked upon as merely tentative in its nature." And some lines above he writes:-" The systematic arrangement of the Opossums has formed the subject of an unusually large number of memoirs, of wdiich the best have been written by Temminck, Waterhouse, and Burmeister. These and all other authors appear, however, to have erred in the admission of by far too great a number of species, formed on the most trivial characters of colour and size, and therefore a large reduction has been found to be necessary in the present work." I perfectly agree with Mr. Thomas as to the great difficulty presented by the group, and I even partly share his opinion that the number of species admitted by former authors is too large and that the synonymy has been much overburdened. But when he chooses the radical method of cutting the Gordian knot by condensing all the species into one and grouping all older synonyms around two varieties only, it seems to m e that he goes too far. O n reviewing the writings of the three principal authors w ho have discussed the Mammals of this region-Burmeisterx 2, 1 ' Systematische Uebersicht der Thiere Brasiliens, welcbe wjibrend einer Beise durch die Provinzen von Rio de Janeiro und Minas Geraes gesammelt ocler beobacbtefc wurden,' vol. i. (1854). 2 ' Erliiuterungen zur Fauna Brasiliens,' Berlin, 1856. |
