394 
AsTEBHDjE.- 
-RADIATA.- 
-Ophiurid^, 
power of reproducitig lost parts when accidentally de- 
stroyed. If an entire arm be torn off, provided a small 
portion of the body remains attached to it, other arms 
are reproduced, and a fresh, perfect animal is formed. 
In each ray we find two ovaries, and it is supposed that 
the animals can reproduce their species without the aid 
of a second individual. The spawn is said to he veno- 
mous to the touch, and poisonous to the animals which 
eat them. The larvae, or young, are very different in 
appearance from the adult animal. They are ciliated, 
and move with great quickness by means of their vibra- 
tile cilia, and swim rapidly, rotating round their axis. 
The order Asteroidea is rather an extensive one, com- 
prising numerous species and many genera, which may 
be arranged in five Families: — I. Anteriidce ; II. Astro- 
pectenidce; III. Pentacerotidce ^ IV. Asterinidce; and 
V. Ophiuridce. 
Family I. — ASTERIID^ {True Sea-stars). 
In this family, the typical Star-fishes, the rays are 
five in number, and they much exceed in length the 
diameter of their disc. The family is represented on 
Plate 6, fig. 2., by A. cylindrica. 
Family II. — ASTROPECTENID.® {Astropectens). 
In this family the back of the rays or arms, which 
are various in number, are- thin and netted, and have 
Solaster papposus. 
numerous tubercles at the junction of each of the little 
bones, which are covered at their tips with many small 
movable spines. They are very beautiful creatures. 
The family is well represented by a species found on 
the coast of England, Astropecten irregularis, the 
“ Asterias aurantiaca” of Muller, and by the Solaster 
papposus, the Rosy Sun-star or Ten-fingers — see fig. 
235 — which, as this latter name indicates, possesses 
ten rays, that nearly equal in length the diameter of 
the disc. 
Family III. —PENT ACEROTIDiE. 
This family is characterized by the body being 
formed of large roundish tubercles, the skin between 
which is pierced with small holes. The genera into 
which the members of this family have been divided, 
are rather numerous. Many of the species have their 
backs studded with conical tubercles, which enlarge in 
size as the part on which they are placed increases. 
These tubercles sometimes fall off as the animal be- 
comes larger, and are easily separated, leaving a flat 
scar when the animal is dead. — {Gray.) 
This family is represented in Plate 6, fig. 3, by 
Pentagonaster pulcliellus, a species which is found in 
the Indian seas. 
Family IV. — ASTERINEDJU {The Birds'- 
foot Stars). 
This, the last family of the Asteroidea, have the body 
formed of compressed pieces, placed one over the other 
like the tiles on a house. They are generally thin, 
flat, and pentangular, have always a thin 
margin, and are covered above and beneath 
with fasciculated spines. Some of the 
species have the back convex, and a few 
are possessed of many rays. 
Family V. — OPHIURID^ {Lizard- 
tailed Star -fishes). 
This family of Echinoderms is char- 
acterized by the species having a more 
or less orbicular, depressed body, with 
five cylindrical, jointed, very flexible arms, 
which are sometimes very long, and re- 
peatedly divided into branches. Their 
arms are furnished with a series of small 
pores along each side of the under sur- 
face, and they have a lunate hole on each 
side of the base of their arms. They 
are scaly, like the tails of serpents or 
lizards, and are very fragile ; hence their 
common English name. They are desti- 
tute of grooves or gutters underneath, 
and have in consequence no tentacles. 
Their motion, therefore, is different from 
that of the true Star-fishes. When they 
move, the animals employ the two arms 
nearest the point to which they wish to 
go, and the one farthest from it. The 
two first, curving at the extremities, form 
two hooks directed outwardly, which applying them- 
selves to the sand, draw the body forwards; whilst 
the posterior arm is curved vertically, and pushes the 
animal along. The species of Lizard-tails live exclu- 
Fig. 236. 
