The Cambrian–Ordovician boundary is a type 1 depositional sequence boundary with dramatic local erosional incision in restricted marine facies on the easternmost New York Promontory. The systemic boundary is bracketed below by Late Cambrian, upper Cordylodus proavus Zone (s.s). conodonts from carbonates of the upper Little Falls Formation (=Whitehall Formation, abandoned). Presumed Lower Ordovician ellesmeraceratoid cephalopods from the upper Little Falls are uppermost Cambrian and among the oldest known in North America. The overlying deepening–shoaling cycle of the Tribes Hill Formation (=Cutting and Great Meadows Formations, abandoned) is the local expression of a lowermost Ordovician (Rossodus manitouensis Zone) depositional sequence recognizable across Laurentia. Complete replacement of conodonts takes place in the late Tremadocian or Tremadocian–Arenigian boundary interval with onlap of the “Fort Ann Formation” across the paleokarst cap of the Tribes Hill. The trilobites Hystricurus sp. and Symphysurina myopia Westrop new species occur in less restricted, thrombolitic facies of the middle Tribes Hill that have the highest conodont diversity. Ulrichodina Furnish, 1938, emend. is regarded as the senior synonym of the conodont Colaptoconus Kennedy, 1994 (=GlyptoconusKennedy, 1980).