Silurian outcrop zones are limited, in the Colomb-Bechar basin, to the Ben Zireg anticline and to exposures resulting from the southern Atlas flexure and bordering faults (Hassi-el-Diab, Teniet-Ghenia). In the area, the Valentian is missing; the Wenlock is transgressive; the Ludlovian is very thin, beginning with the Monograptus deubeli zone; the upper Budnanian and basal Lochkovian (M. uniformis, M. praehercynicus horizons) are present. The Emsian overlies basal Lochkovian beds or lowest Lochkovian, with the Siegenian missing. In general, in the northeast part of the Colomb-Bechar basin the Silurian thins rapidly from south to north. At Hamar Lagdad the Silurian is also condensed; the lower Silurian interval, transgressive on the Caradocian, is upper Valentian; Kopanina and Pridoli equivalents are present while the Lochkovian is represented by intraformational cineritic tuffs which underlie the Hamar Lagdad bioherm (Emsian).