(Ὄκελλος Λευκανός), as his name implies, was a Lucanian, and a Pythagorean in some sense.
Ocellus is mentioned in a letter from Archytas to Plato, which is preserved by Diogenes Laertius (8.80), and in this letter the works above mentioned are enumerated. If the letter of Archytas is genuine, it proves that Ocellus lived some time before Archytas, for it speaks of the descendants of Ocellus. Nothing is said in the letter about Ocellus being a Pythagorean. Lucian (Pro Lapsu, &c. vol. i. p. 729, ed. Hemst.) speaks of Ocellus and Archytas as acquainted with Pythagoras, but we know that Archytas lived at least a hundred years after Pythagoras, and Lucian's historical facts are seldom to be relied on. Ocellus is mentioned by still later writers, but their evidence determines nothing as to his period.[*](GRC: 6/10/08: moved this paragraph up to separate the life from the works and to make this article more consistent with the rest.)
[G.L]