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n. A name given in parts of South America, especially near the mouth of the La Plata river, and in the region of the pampas generally, to a soft concretionary limestone, having about the consistence of slightly baked clay, and of a dark-brown color. It underlies the so-called Pampean formation.

"Where there are large cakes of "tosca" near the surface, as in many localities on the southern pampas, the vizcacha makes its burrow as best he can, and without the regular trenches."