Oolitic and dolarenitic facies of Upper Cambrian and Lower Ordovician formations in Missouri contain abundant algal stromatolites, which are digitate in vertical section and meandrine to subcircular in plan view. Environmental factors and problems of classification are discussed. Application to these structures of the names Collenia or Gymnosolen is decried, and use of simple descriptive terms is supported. Thus the term 'digitate stromatolite' is used for the structures under discussion.