62 
NATURAL HISTORY. 
[n. zool. gal. 
the ambulacra of the Echinidae ; in some, as the Hole « 
thuria , 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 Siphunculidce have many characters in 
common with those animals, but they are destitute of any 
ambulacra. 
The Holothuridce 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 specimens of this order 
in Room VII. 
The Hypostomata, (Cases 11 to 24,) differ from the 
former class in the body being expanded into rays or 
lobed, and in having a bag-like stomach, with 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 Asteroida, (Cases 11 to 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 wart 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 be separated, provided a 
part of the body be attached to it, other arms are repro¬ 
duced, and a fresh perfect animal is formed. Some spe¬ 
cimens illustrative of these facts are in the Case. 
The family of Typical Star-Fishes (Asteriadce), Cases 
11 and 12, have four series of holes and tentacles in each 
of the arm-grooves. Most of the kinds have only two 
series of pores in each groove; they are divided into groups 
of genera, according to the structure of the hard particles 
