Crantor in Harpers Dictionary of Classical Antiquities
（Κράντωρ). A philosopher of Soli, among the pupils of Xenocrates, B.C. 300. He was the first who wrote commentaries on the works of Plato. Crantor was highly celebrated for the purity of his moral doctrine, as may be inferred from the praises bestowed by the ancients upon him. From one of his works, Περὶ Πένθους, Cicero drew largely in writing the third book of the Tusculanae, and the lost treatise De Consolatione on the death of his daughter Tullia. Cf. Cic. Acad. ii. 44.
Crantor in Wikipedia
Crantor (Greek: Κράντωρ, gen.: Κράντορος; died 276/5 BC) was a Greek philosopher of the Old Academy, probably born around the middle of the 4th century BC, at Soli in Cilicia.
Crantor moved to Athens in order to study philosophy, where he became a pupil of Xenocrates and a friend of Polemo, and one of the most distinguished supporters of the philosophy of the older Academy. As Xenocrates died 314/3 BC, Crantor must have come to Athens previous to that year, but we do not know the date of his birth. He died before Polemo and Crates, and the dropsy was the cause of his death. He left his fortune, which amounted to twelve talents, to Arcesilaus. 
His works were very numerous. Diogenes Laertius says that he left behind Commentaries, which consisted of 30,000 lines; but of these only fragments have been preserved. They appear to have related principally to moral subjects, and, accordingly, Horace classes him with Chrysippus as a moral philosopher, and speaks of him in a manner which proves that the writings of Crantor were much read and generally known in Rome at that time. The most popular of Crantor's works at Rome seems to have been that "On Grief" (Latin: De Luctu, Greek: Περὶ Πένθους), which was addressed to his friend Hippocles on the death of his son, and from which Cicero seems to have taken almost the whole of the third book of his Tusculan Disputations. The philosopher Panaetius called it a "golden" work, which deserved to be learnt by heart word for word. Cicero also made great use of it while writing his celebrated Consolatio on the death of his daughter, Tullia; and several extracts from it are preserved in Plutarch's treatise on Consolation addressed to Apollonius, which has come down to us. Crantor paid especial attention to ethics, and arranged "good" things in the following order - virtue, health, pleasure, riches.
Crantor was the first of Plato's followers who wrote commentaries on the works of his master. He also made some attempts in poetry; and Diogenes Laertius relates, that, after sealing up a collection of his poems, he deposited them in the temple of Athena in his native city, Soli. He is accordingly called by the poet Theaetetus, in an epitaph which he composed upon him, the friend of the Muses; and we are told, that his chief favourites among the poets were Homer and Euripides.