The name Mayaguez Group is abandoned because it is no longer valid in the sense in which it was originally defined by Mattson (1960). His Mayaguez contained 7 lithofacies: the Parguera Limestone, here revised; the Brujo Limestone, here abandoned because it is identical to the Cotui Limestone; Melones Limestone, revised; the Yauco Mudstone, revised; the Sabana Grande Andesite, revised; El Rayo Volcanics, revised; and Maricao Basalt, not discussed. The El Rayo Volcanics are not within the Mayaguez but overlie rocks assigned by Mattson to the San German Formation, which does not overlie the Mayaguez, but is equivalent to part of the Mayaguez.

Source: GNU records (USGS DDS-6; Reston GNULEX).

The Melones Limestone occurs in southwestern Puerto Rico and consists of volcanic sandstone interbedded with shaly limestone, calcareous mudstone, and carbonaceous limestone. Estimated thickness is 300 meters. The Melones is of Late Cretaceous age.

Source: GNU records (USGS DDS-6; Reston GNULEX).