Name of Zoophyte Depth in Fathoms Country and S. Latitude Authority Sertularia 40 Cape Horn 66° (Where none is given, the observation is my own.) Cellaria Ditto Ditto Cellaria. A minute scarlet encrusted species, found living 190 Keeling Atoll 12° Cellaria. An allied, small stony sub-generic form 48 S. Cruz River 50° A coral allied to Vincularia, with eight rows of cells 40 Cape Horn Tubulipora, near to T. patima Ditto Ditto Ditto 94 East Chiloe 43° Cellepora, several species, and allied sub-generic forms 40 Cape Horn Ditto 40 and 57 Chonos Arch. 45° Ditto 48 S. Cruz 50° Eschara 30 Tierra del Fuego 53° Ditto 48 S. Cruz R. 50° Retepora 40 Cape Horn Ditto 100 C. Good Hope 34° Quoy and Gaimard, _Ann. Scien. Nat.,_ t. vi, p. 284. Millepora, a strong coral with cylindrical branches, of a pink colour, abut two inches high, resembling in the form of its orifices M. aspera of Lamarck 94 and 30 E. Chiloe 43° Tierra del Fuego 53° Coralium 120 Barbary 33° N. Peyssonel in paper read to Royal society May 1752. Antipathes 16 Chonos 45° Gorgonia (or an allied form) 160 Abrolhos on the coast of Brazil 18° Capt. Beechey informed me of this fact in a letter. Although the limit of depth, at which each particular kind of coral ceases to exist, is far from being accurately known; yet when we bear in mind the manner in which the clumps of coral gradually became infrequent at about the same depth, and wholly disappeared at a greater depth than twenty fathoms, on the slope round Keeling atoll, on the leeward side of the Mauritius, and at rather less depth, both without and within the atolls of the Maldiva and Chagos Archipelagoes; and when we know that the reefs round these islands do not differ from other coral formations in their form and structure, we may, I think, conclude that in ordinary cases, reef- building polypifers do not flourish at greater depths than between twenty and thirty fathoms. It has been argued[37] that reefs may possibly rise from very great depths through the means of small corals, first making a platform for the growth of the stronger kinds. This, however, is an arbitrary supposition: it is not always remembered, that in such cases there is an antagonist power in action, namely, the decay of organic bodies, when not protected by a covering of sediment, or by their own rapid growth. We have, moreover, no right to calculate on unlimited time for the accumulation of small organic bodies into great masses. Every fact in geology proclaims that neither the land, nor the bed of the sea retain for indefinite periods the same level. As well might it be imagined that the British Seas would in time become choked up with beds of oysters, or that the numerous small corallines off the inhospitable shores of Tierra del Fuego would in time form a solid and extensive coral-reef. [37] _Journal of the Royal Geographical Society,_ 1831, p. 218. Chapter V THEORY OF THE FORMATION OF THE DIFFERENT CLASSES OF CORAL-REEFS