Agatharchides

Agatharchides or Agatharchus was a Greek historian and geographer. He lived in the second century BC.
Life.
Agatharchides is believed to have been born at Cnidus. He was later a secretary to Heraclides Lembus.
Agatharchides wrote a few words about his own life. At the conclusion of his book "On the Erythraean Sea", he apologizes for being unable to complete his work "since our age is unable to similarly bear the toil" and "as a result of the disturbances in Egypt" he could no longer access the official records (a fragment cited by Photius in his "Bibliotheca" Cod. 250.110, 460b). 
Writings.
Agatharchides was not well known in ancient times. Of his two major works, "Affairs in Asia" ("Ta kata ten Asian") in ten books, and "Affairs in Europe" ("Ta kata ten Europen") in forty-nine books, only a few fragments survive, too few to provide us with any sense of the contents of either work. However, for his "On the Erythraean Sea" ("Peri tes Erythras Thalasses" or "De Mari Erythraeo") in five books, almost the entire fifth book, a geographical treatise on the Horn of Africa and the lands around the Red Sea, has survived almost intact. According to Burstein, "the comparative soberness of Agatharchides' treatment compared to previous accounts and the wealth of information contained in it led to a quick recognition . . . [that it was] a valuable summary of the results of Ptolemaic exploration."
In the first book of "On the Erythraean Sea" was a discussion respecting the origin of the name. In the fifth Agatharchides described the mode of life amongst the Sabaeans in Arabia, and the Ichthyophagi, or fish-eaters, the way in which elephants were caught by the elephant-eaters, and the mode of working the gold mines in the mountains of Egypt, near the Red Sea. His account of the Ichthyophagi and of the mode of working the gold mines, has been copied by Diodorus (iii.12-18). Amongst other extraordinary animals he mentions the camelopard, which was found in the country of the Troglodytae, and the rhinoceros.
An Agatharchides, of Samos, is mentioned by Plutarch, as the author of a work on Persia, and one περὶ λίθων. J.A. Fabricius, however, the true reading is Agathyrsides, not Agatharchides. 
Namesake.
The crater Agatharchides on the Moon is named in his honour.