Three are a number of simple Cheilostomata which develop avicularia distinctly larger than the zoœcia and more or less constricted in the middle by prominent masses apparently due to infolds of the side walls. Eschara Lesueuri, Hag., sp., is a good example, and others have been figured by D'Orbigny. Similar forms are not uncommon in the English Chalk, but it is curious that all the foreign forms seem to be of branching Biflustrine habit, while all the English species I have yet met with form unilaminate sheets.