A brief history of the systematic position of Opilio saxatilis (C. L. Koch) is given. The genitalia of O. saxatilis and O. parietinus are described, that of the males in more detail since this sex shows the greatest differences. The external characters of the two species are reviewed and compared. Records of O. saxatilis are given and its distribution is discussed, and the ecology of this species is contrasted with that of O. parietinus. It is claimed that sufficient evidence exists for regarding O. saxatilis as a distinct species.