The author directed attention to the following list of species, which, although imperfect, exhibits great variety in the forms, shewing the Medway to be very fertile in these organisms.

Some of the species in this list have been described as new to Britain by Mr Roper, in a late paper published in the Microscopical Journal. The Coscinodiscus, not named, seems from the description to be the same with that found at the mouth of the Thames, and is an exceedingly beautiful disc. The four species of Actinoptychus are those described by Ehrenberg, and are new British species. They exhibit the strong siliceous cellular tissue underneath the moniliform structure of the surface, as in Actinocyclus.