Introduction—I much regret that in the preparation of the present paper I have not, as on the occasion of my former contribution towards the history of the Madreporaria of the Jurassic formation, had the advantage of repeated personal investigations of the strata from which the specimens were obtained. This expression of regret, however, may perhaps seem unnecessary after the appearance of the very ample and able paper on the Corallian rocks of England by Messrs. Blake and Hudleston; but I would observe that as their conclusions were drawn rather from the study of the Mollusca and Echinodermata than from that of the Corals, we are yet in ignorance respecting the exact stratigraphical position of the latter. Consequently it is not by any means certain that the conclusions arrived at by these geologists might not have undergone some modification if the Corals had received more careful examination. Possibly more than one Coralliferous period might have been observed in the Corallian beds, just as more than one has been pointed out in the Inferior Oolite; and as some Madreporarian forms are peculiar to the Coral Rag, it would be interesting to know more fully than we at present do their range in time. It has always been a matter of some surprise that while the Coral Rag of this country fulfils so completely the conditions of a Coralliferous deposit, and is in so many places crowded with Corals, the number of species should be so small. MM. Milne-Edwards and number of species