The old Commentary on the Tipitaka which contained the Mahāvihāra tradition.
It was supposed to have been compiled by, or at least under, Mahinda.
Buddhaghosa learnt it under Sanghapāla and retranslated it into the Magadha (Pāli) tongue, while living in the Ganthākara-parivena (Cv.xxxvii.228-234).
It evidently contained a great deal of historical material as well.
For its nature and contents see MT. Introd. lvii ff.