A second South Caucasian tribal union emerged in the thirteenth century BC on the Black Sea coast. According to most classic authors, a district which was bounded on the south-west by Pontus, on the west by the Black Sea as far as the river Corax (probably the present day Bzyb River, Abkhazia, Georgia), on the north by the chain of the Greater Caucasus, which lay between it and Asiatic Sarmatia, on the east by the Kingdom of Iberia and Montes Moschici (now the Lesser Caucasus), and on the south by Armenia. The westward extent of the country is considered differently by different authors: Strabo makes Colchis begin at Trabzon, while Ptolemy, on the other hand, extends Pontus to the Rioni River.