Cbinoidea.- EADIATA. Holothukoidea. 395 
sively in sandy shores, and hide themselves in the 
mud at the least appearance of danger. Like the true 
Star-fishes, if these animals lose their arms, they are 
able quickly to renew them ; and during summer a few 
days siifiice to replace their loss. 
THE TEUE LIZAED-TAIIS ( Opldura) have the body 
covered with spines or scales ; and the arms, which 
are always simple, are furnished with cross series of 
spines on the sides, which in some of the species are 
short and appressed, in others long and expanded. 
These arms, or rays, are almost always five in number, 
and e.xtremely flexible, though composed of rigid and 
fragile plates. The family is represented on Plate 6, 
fig. 1, by Opldura mutica; fig. 3, 0. squamosa \ fig. 
4, 0. Lamarclcii; and fig. 2, Euryale simplex‘s and on 
Plate 6, fig. 1, by OpMothrix lineolata. 
THE GOEGON-HEADS, or MEDUSA-HEADS (^Astro- 
phyton), have the arms repeatedly branched, so as to 
end in very small flexible filaments, by means of which 
the animal attaches itself to marine bodies, and strains 
its food from the surrounding water. It is from this 
extraordinary branched disposition of the arms that 
the species have derived their name. 
THE COMMON MEDUSA’S HEAD {Astrophyton 
arhorescens) is a native of the North Sea, and has 
been particularly noticed by some of our early arctic 
voyagers. 
Order III. — CEINOIDEA {Feather-stars). 
The order Crinoidea is characterized by the species 
composing it bemg furnished with five arms, which 
bifurcate so close to their origin as to appear like ten. 
These arms are long, slender, jointed, the joints being 
composed of calcareous matter, and furnished with a 
series of processes on each side like a feather; hence 
their English name. In most of the species these 
arms, besides being divided at their base, are repeatedly 
subdivided as they approach their termination. The 
body of the animal is surrounded with hard shelly 
plates. This order of Echinoderms contains several 
families and an immense number of species; but with 
few exceptions these are fossil. To geologists they 
are particularly interesting, as their remains are found 
in vast abundance in the limestone formations, forming 
whole beds of great extent, and composing immense 
strata of what is known as “ entrochal marble,” which 
are found extending ever large tracts of country in 
Northern Europe and North America. Almost all 
these fossil Crinoideans had an elongate peduncle or 
stem, and the joints which composed this stem are 
called entrocld, or wheel-stones. Being perforated in 
the centre, they are well formed for being strung as 
beads ; and in Koman Catholic times, and in Roman 
Catholic countries, they have been used as rosaries. 
In several parts of the north of England these detached 
beads are very common on the sea-shore, and are 
called “ St. Cuthb6rt’s beads.” One of the Fern 
islands, on the coast of Northumberland, was particu- 
larly celebrated as the place where the holy Saint 
Cuthbert manufactured these beads for the use of the 
faithful. The body of the animal is known by the 
general name of “ Encrinite,” or the “ Stone-lily,” 
and a fine collection of these remains, from the moun- 
tain limestone of Yorkshire, exists in the British 
Museum. 
Of this very numerous order of Echinoderms only 
two genera exist, which contain species that are still 
found in the recent form at the present day. The 
species are few in number, and some of them are 
exceedingl}^ rare. 
Family— PENTACRINITID^. 
The animals of this family are composed of two 
kinds — the one having an elongated peduncle furnished 
with claspers, and being fixed by a root to the bottom 
of the sea ; the other existing (in the adult state) as a 
free animal, swimming at will through the water. 
Genus Pentacrinus. — This genus contains the first 
kind. The peduncle, to the top of which the star or 
body is attached, and by the base of which it is fixed 
as by a root, is a long column, formed of numerous 
pentangular joints, and has five auxiliary side arms 
formed of round joints, proceeding from it at intervals. 
At the upper extremity of this column is what is called 
the pelvis, composed of five plates, from which ten 
arms proceed, each subdividing into three fingers. 
THE PENTACEINUS CAPUT-MEDUSAJ is the only 
recent species knowm, and individuals appear to be 
exceedingly rare in collections. It is a native of the 
West Indian seas, and three fine specimens may be seen 
in the British Museum. In none of the four or five 
individuals, which are all that are known to exist in 
museums, is the base of the stem perfect. We have 
thus no positive knowledge as to whether it adhered 
by a fixed base or had a locomotive power. Some 
authors indeed assert that this Pentacrinus is an animal 
that crawls along the bottom of the sea; but from 
the appearance of the peduncles and the analogy the 
species hears to some of the fossil ones, it is much 
more probable that it adheres by its base to some ex- 
traneous matter, and that it stands more or less erect 
in the sea, bending down so as to yield to the force of 
the waves, and rising again when the storm is over. 
Genus Comatula, or Feather-star. — This genus 
is the second kind of animal belonging to the family 
PentacrinilidcB. The body in this genus is orbicular, 
depressed, and very small. It is protected above by 
an assemblage of calcareous pieces, and provided with 
five great rays, deeply bifid and pinnate, and one or 
two rows of short, accessory, articulated, simple rays, 
hj^ means of which the animal attaches itself to foreign 
bodies. The buccal or labial channel is continued 
throughout the whole length of the axis and pinnacles 
of the great rays, is fleshy, and is provided with cirrhi, 
which serve the animal to seize its prey. 
THE ROSY PEATHER-STAR {Comatula rosea) has 
been long known as a native of the British seas. Its 
history is exceedingly interesting, but we must refer 
to the writings of Mr. J. V. Thompson, Professor E. 
Forbes, &c., for further information. 
Order IV. — HOLOTHUKOIDEA {Sea-cucumhers). 
The animals belonging to this order of Echinoderms 
have many characters in common with the Echinidm: 
