During routine analysis of some calcareous and siliceous microbiotas from the London Clay Formation of southeast England (Wilkinson, 2004a, b), some extremely well-preserved, dinoflagellate cysts were observed. These are all large, chorate (spine-bearing) forms, the overwhelming majority of which are referable to Cordosphaeridium gracile (Eisenack, 1954) Davey & Williams, 1966 (Fig. 1). This observation confirms that paly-nomorphs can be extracted effectively from clay-rich samples using a combination of clay deflocculation and sieving, as described recently by Riding & Kyffin-Hughes (2004).

The London Clay Formation from 25 localities in southeast England was processed for calcareous...

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