Note 18 — Chapter XVI · ON TO MATHURÂ OR MUTTRA. CONDITION AND CUSTOMS OF CENTRAL INDIA; OF THE MONKS, VIHÂRAS, AND MONASTERIES.
James Legge translation
There was a Kâśyapa Buddha, anterior to Śâkyamuni. But this Mahâkaśyapa was a Brahmân of Magadha, who was converted by Buddha, and became one of his disciples. He took the lead after Śâkyamuni’s death, convoked and directed the first synod, from which his title of Arya-sthavira is derived. As the first compiler of the Canon, he is considered the fountain of Chinese orthodoxy, and counted as the first patriarch. He also is to be reborn as Buddha. Eitel, p. 64.