114 CORALS AND CORAL ISLANDS. 
cies; and Millepora alcicornis is an identical species, though 
different in variety. 
The Bermudas are in the North Atlantic subtorrid region, 
in the range of the Gulf Stream. The few reef-making spe- 
cies that occur there are all West Indian. The principal among 
them are: Lsophyllia dipsacea, f. rigida, Astrea ananas, Di- 
ploria cerebriformis, D. Stokesi, Meandrina labyrinthica, M. 
strigosa, Orbicella cavernosa, Oculina diffusa, Oculina varicosa, 
Oculina pallens, Oculina Valenciennes, O. speciosa, Siderastreea 
radians, Mycedium fragile, Porites clavaria, P. astreoides, 
Millepora alcicornis ; and the common West India Aleyonoids, 
Gorgoma flabellum, Plexaura crassa Lx., Pl. flecuosa Lx., Pl. 
homomalla Lx., Pterogorgia Americana EKhr., Pt. acerosa Ehr. 
The facts presented are sufficient to show that temperature 
has much to do with the distribution of reef-corals in latitude, 
while proving also that regional peculiarities exist that are not 
thus accounted for. 
UW. DISTRIBUTION IN DEPTH. 
(uoy and Gaymard were the first authors who ascertained 
that reef-forming corals were confined to small depths, contrary 
to the account of Foster and the early navigators. The mis- 
take of previous voyagers was a natural one, for coral reefs 
were proved to stand in an unfathomable ocean; yet it was 
from the first a mere opinion, as the fact of corals growing at 
such depths had never been ascertained. The few species which 
are met with in deep waters appear to be sparsely scattered, 
and nowhere form accumulations or beds. 
The above-mentioned authors, who explored the Pacific in 
the Uranie under D’Urville (and afterward also in the As- 
trolabe), concluded from their observations that five or six 
fathoms (30 or 86 feet) limited their downward distribution. 
