135 
NORTH ZOOL. GAL.] NATURAL HISTORY. 
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 tentactes in each 
of the arm-grooves. Most of the kinds have only tw r o 
series of pores in each groove; they are divided into groups 
of genera, according to the structure of the hard particles 
which form the support of the body, and w 7 hich generally 
agree with the external form of the body. 
The family of Astropectenidce (Cases 13 and 14,) have 
the back of the rays thin and netted, with numerous tuber¬ 
cles at the junction of each of the little bones, which are 
covered at their tips with numerous small moveable spines. 
They are the most beautiful of the order. 
The family of Pentaceridce (Cases 15 to 17,) have the 
skeleton formed of large roundish tubercles, the skin be¬ 
tween wdiich is pierced with small holes ; some of these 
have a convex back and triangular arms, as the Pentace - 
roa; others are flat above and beneath, with five broad, 
short rays edged with larger pieces, as Gomaster ; many 
of these have their back studded with conical tubercles, 
which enlarge in size as the bone on which they are placed 
increases ; these tubercles sometimes fall off as the animal 
increases in size, and are easily separated, leaving a flat 
scar when the specimen is dead. Some of them, as the 
Dactylosaster , Case 17, have elongated cylindrical arms. 
The last family, or the Asterinidce , have the skeleton 
formed of compressed pieces, placed one over the other 
like the tiles on a house ; they alw 7 ays have a thin mar- 
