Mnaseas is reckoned to have been a pupil of a scholar who was chief librarian at what library?
Eratosthenes Eratosthenes of Cyrene ( ; Greek: Ἐρατοσθένης ὁ Κυρηναῖος , ] ;  – ) was a Greek mathematician, geographer, poet, astronomer, and music theorist. He was a man of learning, becoming the chief librarian at the Library of Alexandria. He invented the discipline of geography, including the terminology used today.
Dionysius of Lamptrai Dionysius (3rd century BC) of Lamptrai was an Epicurean philosopher, who succeeded Polystratus as the head ("scholarch") of the Epicurean school at Athens c. 219 BC. He died c. 205 BC and was succeeded by Basilides.