The abundance of hexactinellid sponges in the Chalk (Cretaceous) of the area from Oxfordshire to Hertfordshire northwest of London, England, is significant for estimating the depth of water at the time of deposition. Former work has placed the depth at 100-500 fathoms; it is considered here that the depth was at least 100 fathoms but perhaps not much more.

You do not currently have access to this article.