270 THE OCEAN WORLD. 
very common on every shore, and have been remarked by fishermen 
from the earliest times on account of their singular form, the dis- 
position of their arms, which resemble the tail of a lizard, and by 
the singularity of their movements. The general characteristics of 
this remarkable group of Echinodermata, as described by Dujardin 
and Hupé, are as follows :—They are radiate marine animals creeping 
at the bottom of the sea or upon marine plants. In form they 
present a sort of coriaceous disc, which is either bare or covered with 
scales, which contains all the viscera, and has articulated to it five 
very flexible simple or branching arms, each supported by a series of 
calcareous internal pieces; they are naked or covered with granules, 
scales, or spines. The mouth is situated in the middle of the lower 
surface of the disc, and opens directly into a stomach which is in the 
shape of a sac; it is circumscribed by five re-entering angles corres- 
ponding with the intervals between the arms, having a series of 
calcareous pieces, which perform the function of foot jaws. The 
mouth is prolonged by five longitudinal clefts, which correspond to 
the arms, and are garnished with papillz or calcareous pieces. A 
series of calcareous pieces, somewhat rib-shaped, spring from the 
extremity of each of these clefts, which occupy all the interior of 
the arms, having a furrow in the middle of the ventral surface for 
the reception of a nutritive vessel; and laterally between their ex 
pansions are certain openings, from whence issue the ambulacral 
feet; the visceral cavity opens by one or two clefts on the ventral 
surface of each side of the base of the arms. 
The Ophiuride move themselves by briskly contracting their 
arms so as to produce a succession of undulations analogous to those 
by which a serpent creeps along. Some of these Echinoderms are 
rather active; but others attach themselves by their arms to the 
branches of certain Gorgonide, and remain immovable for a consider- 
able time, waiting their prey somewhat like a spider in the midst of 
his web. 
The family of Ophiuride is divided into two great sections: that of 
the Ophiurine, which comprehends several genera, amongst others 
that which gives its name to the family; and that of the Euryaline. 
The family of Ophiurinz forms a group distinguished by their five 
simple, articulated, very mobile, and non-ramified arms, each of 
which is attached to a small disc or shield plate, with flexible thread- 
like cirri between the rays. The genus Ogfzura is very common, and 
has been known from very early times in European seas. The species 
are often of a greenish colour, with transverse bands, which become 
more obscure upon the arms as the distance from the disc increases. 
