114 
DErTH AT WHICH 
Cm IV. 
MM. Quoy and Gaimard 1 believe that the growth 
of coral is confined within very limited depths ; and 
they state that they never found any fragment of an 
Astrtea (the genus they consider most efficient in form- 
ing reefs) at a depth above 25 or 30 feet. 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 15 fathoms (or thrice 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 2 states that on the Bahama 
banks he dredged up considerable masses of Mean- 
drina from 16 fathoms, and has seen this coral growing 
in 20 fathoms. 
Captain Beechey informs me that branches of pink 
and yellow coral were frequently brought up from be- 
tween 20 and 25 fathoms off the Low atolls ; and Lieut. 
Stokes, writing to me from the N.W. coast of Australia, 
says that a strongly branched coral was procured there 
from 30 fathoms : unfortunately it is not known to what 
genera these corals belong. 
Although the limit of depth, at which each particular 
kind of coral ceases to exist, is thus far from being 
accurately known : yet when we bear in mind the 
1 Annales des Sci. Nat. tom. vi. 
8 Remarks on Coral Formations, p. 12. 
