Recently I reported the presence of the chacoan batrachian Leptodactylus bufonius in the clayey soils of Jarilla, Alto Pencoso and Balde in San Luis, central Argentina (1955, Copeia (4); 291). The possibility was considered that this frog shares the underground social burrows of the rodents of the Lagidium group (vizcacheras) also found analogously in the true chacoan biocenosis. I can state now that some of the rodent communities observed in this xeric area are those of Lagostomus maximus (vizcacha pampeana); also there are many burrows of Galea (cuis) and Microcavia (Cavidae of the Kerodon group) as in the plains of La Rioja.