200 MR. HOLDSWORTH ON THE DISTRIBUTION OF CORALS.| June 24, 
the British Museum are several specimens of this coral which were 
brought from Sicily. These are all attached to a species of Turri- 
tella. The occurrence of this second species of Caryophyllia in 
three distinct localities on our coasts entitles it to a place among our 
British corals; and further investigation will probably show it to be 
generally distributed in the deep water along our western shores. 
It may not be uninteresting to inquire here into the distribution 
of corals around the British Islands, and to trace, as far as possible, 
the cause of their frequenting only particular lines of coast. 
The existence of the coral-polype in our seas is mainly dependent 
on the warmth and purity of the water. A tolerably high tempera- 
ture is undoubtedly one of the most necessary conditions for the well- 
being of the delicate polypes whose calcareous lamellated skeletons 
constitute the true stony corals. Only within the tropics do we meet 
with those vast reefs and extensive accumulations of coral-growth 
which form so characteristic a feature of the seas in those warm lati- 
tudes. The surface-water there becomes heated by the direct influ- 
ence of the sun, and, in those regions, few coral-polypes carry on 
their ceaseless work at a greater depth than 30 fathoms, thence 
building upward to the lowest tide-mark. As we come towards more 
temperate regions, the species diminish both in size and number ; 
simple forms become proportionately more numerous, and their ba- 
thymetrical range is greatly increased. 
The waters of north-western Europe might be expected generally 
to be too much within the influence of Polar temperature to be fitted 
for coral-life, even in its simplest form ; yet in our own seas, and 
extending far into the Arctic Ocean, are found some few species 
vying with the productions of the Tropics in brilliancy of colouring 
and delicacy of structure. Here, however, we have a peculiar and 
extraneous source of warmth in the Gulf Stream, whose waters, now 
becoming widely diffused, but still retaining some portion of their 
original excessive temperature and motion, exercise a sensible influ- 
ence on the coast-productions of the western side of the British 
islands. The course of the current in the neighbourhood of our 
shores is marked sparingly, but distinctly, by the presence of eight or 
ten species of living coral. 
The long list of habitats recorded by Mr. Gosse in his valuable 
‘ Actinologia Britannica’ has been of great use to me in tracing the 
range of our native species; and although many parts of the coast 
have been but little worked, enough has been done to furnish a 
tolerably clear outline of the distribution of the coralligenous polypes. 
From the writings of Maury and others, it appears that the Gulf 
Stream is divided by the British Islands; one portion going south- 
ward to the Bay of Biscay, the other and main body of the current 
sweeping away to the north by the Orkneys and Shetland. The 
entrance of the English Channel and the Irish Sea would thus be 
under the most direct influence of the warm current ; and it is in these 
waters we find corals most abundant. Devonshire and Cornwall are 
extremely rich in these productions ; and, including Weymouth Bay 
(the only recognized locality for Hoplangia durotrix), the south- 
