This book is intended as a textbook for the students of systematic ichthyology for the use in universities, colleges and technical fishery institutes based on series of lectures given by the author at the university of Moscow. The course acquaints the students with the living habits of individual groups and species of fish; classification of fish and knowledge of the evolution of individual groups and their distribution. It also gives the necessary basic information which serves to solve practical problems of the fishing industries. The fundamental biological data pertains to the commercial fish of the USSR adjacent and other waters. The particular attention is given to those groups that are of general interest.