Gallery, 
No. 10. 
Corals. 
Wall-cases, 
Nos. 1 to 5, 
aud 
Table-cases. 
Nos. 1 to 8. 
Compound 
Corals. 
Actinozoa — Corals. 
The number of the septa varies in the several diy ,R mn* ’ 
thus in the Aporosa and Perforata they are m ^ 
of six, whilst in the Rugosa there are usually fom pnma.y 
SeP Havin<>' briefly described a simple coral polype with its theca 
or external wall,' its septa corresponding to the mesenteries ot 
the sea anemone, we can better understand an aggregate coral, 
built up by a large number of these simple polypes growing 
together and uniting their separate calcareous skeletons so as to 
form a compound corallum. The colony may consist of ft 
number of individuals, all springing directly from one another, 
or they may be united by a common flesh or ccenosarc. ™ 
ccenosarc secretes a common calcareous basis or tissue, wl 
unites the several corallites together, called the ccenenchyma. 
Some coral polypes increase their mass by lateral gemmation, or 
budding from the sides; others from the base by root-hkc pio- 
lonoations ; or new individuals are developed by budding Within 
thelup of the parent polype (known as cahcular gemmation), as 
in tl/e genera Lonsdaleia, OomophylUm, Ac.; whilst others 
increase by fission of the parent polypes themselves 
\A\ the Irvin" Zoantharia sclerodermata inhabit the sea, ana 
no doubt all the fossil corals were also marine. They attain 
their maximum development at the present day in the warmer 
seas of the globe, so that their abundant presence m any forma- 
tion may be accepted as good evidence of the former existence 
of a warm temperature in the sea of that period Two 
distinct trees of corals exist at the present day, namely, those 
which inhabit tolerably deep water, and those which build the 
great masses of corals which are known as coral-reefs The 
deep-sea corals often attain, as individuals, considerable size ; 
thpv also orow as compound masses, hut never form those 
massive aggregations known as “reefs.” Deep-sea corals 
an near to have existed in all the great geological periods, from 
the Ordovician upwards. The chief gene >a of this group now 
livino- are Caryophyllia , B ala, nophy Ilia, Flabellum , Desmophyllum , 
and Sphenotrochus, all simple forms ; and Lophoheka , Amphiheha, 
Dendrophyllicb, and Astrangia, compound forms. 
The great majority of the reef-bmlders are compound forms, 
and those of Secondary, Tertiary, and Recent times, belong to 
the families of the Astrceidce, PoritidcB, and Madrepondce, though 
the Ocuknidce and Fungidce also contribute to form reefs. 
If coral-reefs existed in Palaeozoic times, they were built up 
bv Ruo-ose corals. In Mesozoic times true reefs certainly 
existed at the close of the Trias, and especially in Oolitic times 
in Western Europe and England. In early Tertiary times vast 
* From (T/cXrjpog, hard, aud kpna, kp, tarot;, shin: applied to the coral- 
lum which is formed within the tissues of the sclerodermic corals. 
