“Siddham”（悉曇、悉檀、悉談・Xitan）is the general name for a type script used for writing Sanskrit. “Siddham Chapters” （悉曇章 Xitan Zhāng / S.C）are texts that describe the styles of Sanscrit writing, present tables of characters, discuss the special meanings of Characters, and discribe spelling, grammer, and pronunciation. Several varieties of Siddham Chapters are seen in the Dunhuang manuscripts, among them the “Prajñāpāramitā-hṙidaya-sūtra / S.C”＜般若心経悉談章＞, the “Chan men / S.C”＜禪門悉談章＞, the “Lay-person’s / S.C”＜俗流悉談章＞. These chapters do not siscuss all sixteen of the Siddham mātṙikās, but only four relatively rarely used vowels ṙ, ṙ¯, l̇, l̇¯（魯・留・廬・樓）＜fourmātṙkās 別摩多＞, as distinguished from the twelve more commonly used vowels＜twelve 通摩多＞. The compilers of the Siddham chapters reliedextensively on authoritative texts such as the “Kumārajīva’s syllables” ＜鳩摩羅什法師通韻＞and the “Mahāparinirvāṅa-sūtra S.C.＜涅槃経悉曇章＞. These characteristics apply to the Chan-men. S.C （禅門悉談章），the Subject of this presentation. The full title of this text is the “Siddham Chapter of Zen Teaching of the Laṅkāvatāra-sūtra” ＜佛説楞伽経禅門悉談章＞translated by Zen master Din-hui 定慧禅師 of the temple Kuaishan-si 会善寺 on Mount Song 嵩山. There are seven extant texts of Chan-men in the Dunhaung manuscripts, namely Pelliot 2204, 2212,3082, and 3099 ; Stein 4583 ; BD 00041, 俄 Dx00492. This presentation addresses following issues : 1） the relation between Laṅkāvatāra-Sūtra and the Chan-men. S.C. 2） the back ground of the Zen thought” Chan-men” : and 3） the poetic expression of Zen thought and the manner in which this expression developed through the use of popular songs歌謡. The final goal of my research to produce a fully revised text of the Chan-men, S.C.
