EOHINODEEMATA. 
279 
Ophujeabj! . 
Tile Ophiuras are thus named from two Greek words (odu'i, a 
serpent, and ovpa, a tail), from their fancied resemblance to the tail 
°f a serpent. These zoophytes are met with in almost every sea, hut 
ehiefly in those of temperate regions ; they are very common on every 
shore, and have been remarked by fishermen from the earliest times 
°u account of their singular form, the disposition of their arms, which 
Kemble the tail of a lizard, and by the singularity of their move- 
ments. The general characteristics of this remarkable group of 
■Echinodermata, as described by Dujardin and Hupe, are as follows : 
They are radiary marine animals creeping at the bottom of the sea, 
° r upon marine plants. In form they present a sort of coriaceous 
hsk, which is either bare or covered with scales, which contains 
all the viscera, and of five very flexible simple or branching arms, 
each sustained by a series of vertebral internal pieces, naked or 
c °vered with granules, scales, or bristles. Certain fleshy tentacu la 
tiuown out laterally are organs of respiration. The mouth is situated 
in the middle of the lower surface of the disk, and opens directly into 
a stomach in the shape of a sac ; it is circumscribed by five re-entering 
a Qgles corresponding with the intervals of the arms, having a senes of 
calcareous pieces, which perform the function of jaw-bones. This 
mouth is prolonged by five longitudinal clefts, garnished with papillae 
° r calcareous pieces, which correspond to one of the arms. A series of 
calcareous pieces in the shape of vertebrae 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 recep- 
tion of a nursing vessel, and laterally between their expansions are 
certain cavities, from whence issue certain fleshy retractile tentacula ; 
visceral cavity opens by one or two clefts on the ventral surface 
of each side of the base of the arms. 
The Ophiuradm move themselves by briskly contracting their arms 
s ° as to produce a succession of undulations analogous to those by 
^hich a serpent creeps along. Some of these zoophytes are rather 
acti ve ; but others attach themselves by their arms to the branches of 
Cei 'tain other polypes, like the Gorgons, and remain immovable for a 
c °muderable time, waiting their prey somewhat like a spider m the 
midst of his web. 
