Crinoidea.- 



-RADIATA.- 



-HOLOTHUROIDEA. 



395 



sivcly in sandy shores, and hide themselves in the 

 niuj at the least appearance of danger. Like the true 

 Star-fislics, if these animals lose their arms, they are 

 able quickly to renew thera ; and during summer a few 

 days suffice to replace their loss. 



THE TRUE LIZARD-TAILS (Ophiura) 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 appre.ssed, in others long and expanded. 

 These arms, or rays, are almost always five in number, 

 and extremely flexible, though composed of rigid and 

 fragile plates. The family is represented on Plate G, 

 fig. 1, by Ophiura mutica; fig. 3, 0. squamosa; fig. 

 4, 0. Lamarchii ; and fig. 2, Euryale simplex ; and on 

 Plate 6, fig. 1, liy Ophiothrix lineolata. 



THE GORGON-HEADS, or MEDUSA-HEADS (Astro- 

 ]iJii/loii), have the arms repeatedly branched, so as to 

 end in very small flexible filaments, by means of which 

 the animal attaclies itself to marine bodies, and strains 

 its food from the snrrounding water. It is from this 

 extraordinary branched disposition of the arms that 

 the species have derived their name. 



THE COMMON MEDUSA'S HEAD [Astroplii/ton 

 arhoresccns) is a native of the North Sea, and has 

 been particularly noticed by some of our early arctic 

 voyagers. 



Order III.— CPvINOIDEA (Feather-slars). 



The order Criiioidea is characterized by the species 

 composing it bf'ng 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 Ijard 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 coimtry in 

 Northern Europe and North America. Almost all 

 these fossil Crinoideans liad an elongate peduncle or 

 stem, and the joints which composed this stem are 

 called ciilrodii, or wheel-stones. Being perforated in 

 tlie centre, they are well formed for being strung as 

 beads ; and in Roman 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 veiy common on the sea-shore, and are 

 called " St. Cuthbert'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 fur the use of the 

 faithful. The body of the animal is known by the 

 general name of " Encriuite," or the " Stone-lily," 



and a fine collection of these remain.s, 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. Tho 

 species are few in number, and some of them are 

 exceedingly 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 PENTACRINUS CAPUT-MEDUS5; is the only 

 recent species known, 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 bears 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 

 Pentacrinilida:. The body in this genus is orbiculai', 

 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, 

 by means of which the animal attaches itself to foreign 

 bodies. The buccal or labial channel is continued 

 throughout the whole length of tlie axis and pinnacles 

 of the great rays, is fleshy, and is provided with cirrhi, 

 which serve the animal to seize its prey. 



THE ROSY FEATHER-STAR {Comatula rosea) has 

 been long known as a native of the British seas. It3 

 history is exceedingly interesting, but we must refer 

 to the writings of IMr. J. V. Thompson, Professor E. 

 Forbes, &c., for further information. 



Order IV.— HOLOTHUROIDEA (Sea-cucumbers). 



The animals belonging to this order of Echinoderma 

 have many characters in common with the Echinida: ; 



