What is "gangaridai"

Gangaridai ( Gangaridae) was an ancient kingdom, which existed around 300 BC, in the Bengal region of the Indian subcontinent. It was described by the Greek traveller Megasthenes in his work Indica. Greek and Latin historians suggested that Alexander the Great withdrew from the Indian subcontinent, anticipating the valiant joint counterattack of the mighty Gangaridai and Prasii ( Nanda) Empires, the latter located in central Bihar. The capital of the Gangaridai was situated at Kotalipara in present-day Gopalganj District, Bangladesh.