Topotypes of Multiplicisphaeridium? sprucegrovensis Staplin have been obtained using modem processing techniques. Examination of these with sophisticated optical and electron microscopes has revealed important morphologic features not recorded in the original description. These data, combined with a restudy of Staplin's holotype and paratype, require a new combination, Craterisphaeridium sprucegrovense. Some specimens attributed in the literature to this taxon may belong to Puteoscortum williereae Martin. The differences that separate these taxa are emphasized. A third taxon, Pertusisphaeridium dispar gen. et sp. nov., is described for the first time. It is similar to C. sprucegrovense comb. nov. in gross morphology but is distinctly different in detail. A new type of excystment structure, the pelecinate median split, is described from this form and is shown to occur also in C. sprucegrovense.

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