v aoTBIH lAHUTAVi [.II MOOJI 
116 NATURAL HISTORY. [n. ZOOL. GAL. 
simple, and their jaws are small or only rudimentary. Only a few kinds 
are now found in a recent state, but the extinct species are very nu¬ 
merous, forming several very distinct genera. The vent in some of 
these is above the hinder margin, but it is never in the middle of the 
back. • 
The family of Spatangid^; (Cases 9, 10) differ from all the others 
in the mouth being transverse, and more or less in front of the middle 
of the under side of the shell. They are destitute of jaws ; the series 
of pores are generally interrupted, but they form petal-like rows, both 
on the back and near the mouth. The shell is generally heart-shaped, 
with a groove from the crown to the mouth in front, and they are some¬ 
times furnished with long slender as well as the usual small short spines. 
The cases or shells of these animals are formed of the same number of 
bands as the other Sea Eggs, but the bands are of unequal breadth, as 
is sometimes the case with deformed specimens of the hemispherical 
Echini. (See specimen in Case 2.) 
The Holothurida, or Sea Cucumbers, have many characters in 
common with the Echinidce , but their skin is only hardened with 
irregular scale-like or oblong bones; their mouth is in general sur¬ 
rounded with five or ten plumose appendages. Most of them are fur¬ 
nished with rows of pores similar to, and for the same purpose as, the 
ambulacra of the Echinidae; in some, as the Holothuria, they form 
regular lines from the mouth to the vent; in others, as the Cuvieria , 
( Case 10,) they are all crowded on the under surface of the body, which 
is in general flat. 
The family of Siphunculid^ have many characters in common with 
those animals, but they are destitute of any ambulacra. 
The Holothurida and Siphunculidce are eaten; the Trepang, a 
common name of the various species of the former genus, is much 
sought after by the Chinese to flavour their soup. Also see the speci¬ 
mens of this order in the Upright Cases in the Fifth Room of this 
Gallery. 
The Hypostomata, (Cases 11—24,) differ from the former class in 
the body being expanded into rays or lobed, and in having a bag-like 
stomach, w ith only a single aperture through which the food is received, 
and the indigestible part rejected. It contains the Asteroida and 
Ophiurida. 
The true Star-Fishes, or \steroida, (Cases 11—18,) have the 
body expanded into arms of the same structure as itself, and the under 
sides of the arms are marked with grooves radiating from the centre, 
pierced with two or four rows of holes, through which are emitted 
filaments with expanded tips, which the animal uses in locomotion, and 
they have a w T art on the back, the use of which is unknown. The 
Asterice differ greatly from one another both in texture and form. 
Most of the species have five rays, but varieties are sometimes met with 
which have only four rays, one of which is in Case 17. Some species 
have eight, others nine, and others again from twelve to thirty rays. 
Most of the species have the faculty of reproducing the arms, or such 
parts of them as may be accidentally broken off; and if an entire arm 
he separated, provided a part of the body be attached to it, other arms 
are reproduced, and a fresh perfect animal is formed. Some specimens 
illustrative of these facts are in the Case. 
