The second volume contains the paleontological and biostratigraphic materials of the Silurian and Devonian in the Sayan Alai fold area. The corresponding two parts of this volume are extremely uneven, which is not only because the Silurian sediments in Sayan Alai region are less developed than Devonian sediments, but also because of the low degree of research on the former. In compiling this volume, we have encountered common difficulties in dividing materials involving transitional deposits between the various systems: there are always mixed fauna and flora in these deposits, and there are always opposite suggestions for classifying these deposits into older or younger systems. This problem has not been solved by modern stratigraphy (we believe that it is mainly due to the forgetting of A. PI Karpinski's proposal to divide the transitional sediments between the systems into independent units). In each specific case, this problem is solved arbitrarily and artificially. Therefore, the contemporaneous sediments in different regions are often classified into different systems. The situation is complicated by the fact that such transitional stratigraphic units are moved up and down indefinitely. The viewpoint of the researchers on the stratigraphic location of the reddian stage can well illustrate this point. In 1888, gosley, in his famous monograph l'ardenne, demonstrated that the redinian belongs to the Lower Devonian. In 1912, Mo leilish described a series of typical Silurian formations from the mengkelepi slate, the main fauna of the zedinian stage. However, in 1920, Xia baluwa, Bao Provo and RI dibuwa severely and persuasively criticized Mo leilish's identification and returned to gosley's point of view. However, in 1934, a fox insisted that the Redding deposits in the Sauerland area belonged to the upper Silurian. Subsequently, the debate on the age of the gedingian period was only further deepened: vaschmitt and rohricht classified it as Devonian, while g. Dammer and B. Bair classified it as Silurian. If the discussion of this problem does not shift to another level pointed out by A. PI. Karpinski and V. o. Kovalevsky, there is absolutely no sign that this problem will be satisfactorily solved. Therefore, there is neither a clear definition nor consensus on how to treat the transitional stratigraphic unit characterized by mixed fauna and flora. For this reason, the editors of this publication (this book was written with the participation of a large number of authors, who sometimes hold opposite views on these stratigraphic units) believe that it is not necessary to adhere to any rigid regulations in this case, but to give authors freedom to a large extent. If the author has no objection, the paleontological materials related to such strata will be elaborated according to the system they belong to in the unified stratigraphic division scheme. This is how we deal with the tomchumeish formation (ostracod rock series, also known as dunskoy zavotsk Rock Series) in the saler region: its fauna is listed in the section on Silurian, although the editors are convinced that these formations belong to Devonian, and this will be obvious to most people in the near future. However, the situation is more complicated for the materials related to the bistelinsk rock series in the minusinsk depression: the flora of the rock series still has typical late Devonian characteristics, which are closely related to the early Late Devonian plant communities, while the fish of the rock series have typical Carboniferous characteristics. Therefore, the material on the bistelinsk rock flora is placed in this volume, while the material on fish is placed in the next volume. The second volume has published many unpublished materials: the materials on bedsheet corals and solar corals were provided by Pu Si Jubo and en wa mironova, the materials on tetrapod corals were provided by VA a gertonogova, the materials on stromatoporoids were provided by fo Ke harlfina, the materials on brachiopods were provided by Le te grazianova, VA G zinchenko and en Pu Kulikov, and so on.