APPENINUS, now the Appennine; a mountain, or ridge of mountains, running through the middle of Italy, from north-west to the south-west for 700 miles, in the form of a crescent, (Pliny); beginning at the Alps in Liguria, or the Riviera di Genoa; and terminating at the strait of Messina, or at Reggio, and the promontory Leucopetra; and separating, as by a back or ridge, the Adriatic from the Tuscan sea, (Pliny, Strabo, Ptolemy, Polybius, Vitruvius). This mountain, though high, is greatly short of the height of the Alps. Its name is Celtic, signifying a high mountain.