The Chalk of England contains three main hexactinellid faunas, of lower Cenomanian, middle and upper Turonian, and lower Senonian to Maestrichtian age respectively. The third is also represented in Ireland. A number of minor faunal changes can also be recognized. The three main faunas have little in common, and their relationship is not evolutionary; the changes appear to be due to migrations. By analogy with modern forms, this is likely to reflect changes in the pattern of current circulation in the upper Cretaceous ocean.