1 32 
l he second order of corals, the Alcyonoida , shown in the south 
half of Case 2, includes the sea-fans, the sea-whips, organ-pipe 
coral, etc. There is not often a limestone skeleton, although this 
is occasionally present, as in the precious red-coral. Usually the 
supporting skeleton contains a horny axis. This may be observed 
in many of the specimens. There are several alcoholic prepara- 
tions of corals and some glass models, which show the organi- 
zation of these interesting animals. 
CRINOIDS, STAR-FISH, SEA-URCHINS, ETC, 
Cases 3 and 4 and Tal)le Cases. — The class of ani- 
mals designated by the term Echinodermata includes the Crin- 
oidea (sea-lilies, etc.), the Ophiuroidea (brittle-stars and basket- 
fishes), the Asteroidea (star-fishes), Echinoidea (sea-urchins), and 
the Holothuroidea (sea-cucumbers). These are exhibited in the 
Wall-cases 3 and 4, and in Table-cases 5, 6, 7, 8, 9 10, 11 and 12. 
The series begins with Table case 5. 
d he class takes its name from one of the most obvious char- 
acteristics of the group — the possession of a covering of spines. 
These spines undergo the most extraordinary modifications, not- 
only in the different groups of the class, but even in different 
parts of the body of some individuals. They are sometimes 
wholly wanting. 
Case 5.— Here are shown the lowest forms of the class, the 
Crinoidea . Many species are furnished with a long stem, by 
means of which the animal is attached to some fixed object. 
Comparatively few species now exist, but in some of the earlier 
geological periods the crinoids were extremely abundant. In 
Wall-case 3 are shown some alcoholic preparations. 
In Case 5 are also exhibited the Ophiuroidea , some of which 
are known under the names brittle-stars and serpent-stars ; others 
as basket-fishes ; although they are in nowise related to true 
fishes. Some of them are remarkable for their very long and 
attenuated arms. The basket fish (A strop hy ton) is remarkable 
for its branching arms. 
Cases 6, 7 ancl 8 and part of 9 — Specimens of the order 
Asteroidea (starfishes). The simplest form of these animals is a 
central disk passing gradually into five arms; but there are ex- 
treme modifications of this pattern. The arms may be more nu- 
