Cretaceous silicoflagellate assemblages from Arctic Ocean USGS Core 437 show Vallacerta siderea the most abundant species; most species of Lyramula disappear halfway up the core; only L. burchardae, n. sp., persists into the upper sections. These occurrences are untypical of the few documented Cretaceous assemblages from other areas. A Campanian or Maestrichtian age is suggested by correlation, but the uniquely high abundance of V. siderea and lack of Corbisema suggests that a difference in both age and general environment could be involved. If Core 437 is latest Maestrichtian, then the evidence from this core would constrain the timing of the ocean-freshening model for the Cretaceous-Tertiary boundary extinctions. ?? 1981 A.M. Dowden, Inc.