Crypta Magna is the remnant of

Medial surface of each tonsil has 15-20 crypts, the largest of which is called Intratonsillar cleft or crypta Magna (which represents the persistence of the ventral poion of the second pharyngeal pouch)'.Ref: PL Dhingra, Diseases of Ear, Nose & Throat, 7th edition, pg no. 291