nineteen years, extending from 568 AH—the year Khwarazm Shah died—to 587 AH, the year Ibn Maghawir al-Shātibī passed away. The deaths of those included in Stratum Thirty-One range from 575 AH, the year Ibn ʿIyād al-Andalusī died, to 601 AH, the year al-Artāḥī passed away, so that stratum covers (26) years. Stratum Thirty-Five, however, spans no more than nine years, for all the individuals listed therein died between 651 and 660 AH (1).

In his work al-Muʿīn fī Ṭabaqāt al-Muḥaddithīn, al-Dhahabī named the earliest strata after their most prominent figures, saying, for example, “the stratum of al-Zuhrī and Qatāda” (2), “the stratum of al-Aʿmash and Abū Ḥanīfa” (3), and “the stratum of Ibn al-Madīnī and Aḥmad” (4), and so forth.

He later abandoned this method when he reached the beginning of the third Islamic century, and began instead to designate each stratum by an approximate span of years, as in: “the stratum consisting of those who survived beyond 300 AH up to about 320 AH” (5) and “the stratum running from the thirties to a little after the fifties of the 500s AH” (6), and so on.

Our examination of these temporal units shows that, in this book, a single stratum may encompass roughly twenty years (7), or twenty-five (8), or