But we have seen that in several places the bottom of the sea is paved with massive corals at more than twice this depth; and at fifteen fathoms (or twice this depth) off the reefs of Mauritius, the arming was marked with the distinct impression of a living Astraea. Millepora alcicornis lives in from 0 to 12 fathoms, and the genera Madrepora and Seriatopora from 0 to 20 fathoms. Captain Moresby has given me a specimen of Sideropora scabra (Porites of Lamarck) brought up alive from 17 fathoms. Mr. Couthouy ("Remarks on Coral Formations," page 12.) states that he has dredged up on the Bahama banks considerable masses of Meandrina from 16 fathoms, and he has seen this coral growing in 20 fathoms. A Caryophyllia, half an inch in diameter, was dredged up alive from 80 fathoms off Juan Fernandez (latitude 33 deg S.) by Captain P.P. King (I am indebted to Mr. Stokes for having kindly communicated this fact to me, together with much other valuable information.): this is the most remarkable fact with which I am acquainted, showing the depth at which a genus of corals often found on reefs, can exist.
We ought, however, to feel less surprise at this fact, as Caryophyllia alone of the lamelliform genera, ranges far beyond the tropics; it is found in Zetland (Fleming's "British Animals," genus Caryophyllia.) in Latitude 60 deg N. in deep water, and I procured a small species from Tierra del Fuego in Latitude 53 deg S. Captain Beechey informs me, that branches of pink and yellow coral were frequently brought up from between twenty and twenty-five fathoms off the Low atolls; and Lieutenant Stokes, writing to me from the N.W. coast of Australia, says that a strongly branched coral was procured there from thirty fathoms; unfortunately it is not known to what genera these corals belong.
(I will record in the form of a note all the facts that I have been able to collect on the depths, both within and without the tropics, at which those corals and corallines can live, which there is no reason to suppose ever materially aid in the construction of a reef.
(In the following list the name of the Zoophyte is followed by the depth in fathoms, the country and degrees S. latitude, and the authority. Where no authority is given, the observation is Darwin's own.)
SERTULARIA, 40, Cape Horn 66.
CELLARIA, 40, Cape Horn 66.
CELLARIA, A minute scarlet encrusting species, found living, 190, Keeling Atoll, 12.
CELLARIA, An allied, small stony sub-generic form, 48, St Cruz Riv. 50.
A coral allied to VINCULARIA, with eight rows of cells, 40, Cape Horn.
TUBULIPORA, near to T. patima, 40, Cape Horn.
TUBULIPORA, near to T. patima, 94, East Chiloe 43.
CELLEPORA, several species, and allied sub-generic forms, 40, Cape Horn.
CELLEPORA, several species, and allied sub-generic forms, 40 and 57, Chonos Archipelago 45.
CELLEPORA, several species, and allied sub-generic forms, 48, St Cruz 50.
ESCHARA, 30, Tierra del Fuego 53.
ESCHARA, 48, St Cruz R. 50.
RETEPORA, 40, Cape Horn.
RETEPORA, 100, Cape of Good Hope 34, Quoy and Gaimard, "Ann. Scien. Nat." tome vi., page 284.
