Leaching of Ordovician cherts from the Southern Uplands using dilute hydrofluoric acid has yielded numerous radiolaria, sponge spicules and a few conodonts. Although many of the radiolaria have suffered intense recrystallisation, it nevertheless proved possible to extract for SEM examination some examples with exquisitely preserved micro-structure. Despite this, the radiolaria have not proved sufficient, on their own, to answer the outstanding biostratigraphical question of one continuous or two separate episodes (Arenig and Llanvirn/Caradoc) of chert sedimentation in the Southern Uplands. This is partly because the biostratigraphy of Lower Palaeozoic radiolaria is still quite poorly known. A new radiolarian species, Protoceratoiciskum clarksoni Danelian, has been identified and described from cherts in the Crawford area. In addition, the distinctive sponge species Konyrium varium Nazarov & Popov, has also been found for the first time in Southern Uplands cherts. This new occurrence, in deep-water sediments, suggests a much wider habitat for this unusual sponge. Amongst the few conodont elements extracted, one can be identified as probably belonging to the genus Periodon.