RADIATA. | 39 
the animal has the power of locomotion, sometimes by means of the 
arms, and sometimes with the aid of the suckertike feet. The arms in 
some genera are provided with numerous lateral filaments, and in some 
eases they divide into branches. The genus Astrophyton (named also 
Euryale and Gorgonocephalus) (pl. 76, fig. 63), is remarkable for its 
five dichotomizing arms sending off branches, and terminating in a multi- 
tude of curled filaments, which, it is said, may amount to eight thousand in 
a single individual. 
The genus Ophiura (pl. 76, jig. 64) is named from the resemblance 
which its jong and slender arms bear to the tail of a serpent, not only in 
form, but in the numerous bony pieces of which they are composed, 
and which are not unlike the scales of a serpent. The arms are very 
flexible; and by giving them an undulating motion, the animal can 
swim to a certain degree. On each side of the base of the arms is an 
opening which is the outlet of the ovaries, of which there are ten. Several 
species inhabit the coast of the United States. In Ophzolepis (jig. 62), a 
genus allied to Ophiura, the disk is entire, with smooth plates. In both 
genera the arms have movable spines, which in some species are appressed, 
and in others projecting. The species figured, 0. scolopendrina, is found 
near the Isle of France. In these genera the mouth is in the centre of the 
ventral surface, and from it are continued five grooves, through which a 
few sucker-like feet are projected. The mouth is armed with a strong 
osseous apparatus for masticating food. The arms, when broken off, can 
be reproduced. PI. 76, fig. 61, represents Astrogonium granulare of the 
seas of northern Europe. In this genus the rays are not so well developed 
as in Asterias (fig. 60), which gives it a pentagonal figure. 
Oreaster turritus (pl. 76, fig. 59) attains a length of ten inches, and 
inhabits the Indian Ocean. 
Solaster is distinguished by an increased number of rays; S. papposus 
(pl. 76, fig. 66) isa foot in diameter. 
Stellonia rubens (fig. 65) attains a foot in size, and is so abundant in the 
seas of Europe as to be spread over the soil as a manure. 
Asterias (fig. 60) has the rays so much enlarged that there is room in 
the coneavity of each for two extensions or appendages of the stomach, 
with an ovary between them, and a liver; which is not the case in the 
slender rayed genera like Ophiurus. Moreover, the size of the rays renders 
them less flexible, and badly fitted for locomotion ; but as a compensation, 
they are pierced along their inferior surface (between short transverse bones 
arranged in series on each side of a deep central groove) with a multitude 
of ambulacral perforations, through which the feet already mentioned project, 
and which enable the animal to crawl up a surface as smooth as glass, and 
also assist in holding its prey. The sucker-like feet are connected 
within the aperture through which they project, with a globular vesicle 
filled with water, by the hydrostatic action of which the suckers are extended 
or withdrawn. Each vesicle is connected by a small tube with a canal 
which traverses each ray, starting from a circular canal around the 
cesophagus. 
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