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are scales and spinules on them close to the tentacular openings. 
These are small and broad as a rule, single or multiple, and 
occasionally, some are on the lower arm plate. Their duty is 
to protect the base of the tentacles. A third kind of spine is 
noticed in the small group of Ophiurans which clasp by bend- 
ing their arms downwards. These spines are really hooklets, with 
two or more sharp recurved brilliantly transparent teeth, and the 
side arm plates resemble flaps stretching out from the arms 
more than anything else. Similar, but less elaborately orna- 
mented, hooks are found in many Brittle Stars, and usually 
the spine next to the tentacle is thus formed. Some Sand 
Stars, such as Ojphioglyjpha , have a hooklet near the end of 
the arm instead of one of the spines, and Mr. Percy Sladen 
has found them in our North Sea forms. 
Almost every naturalist has read Edward Forbes’s account 
of the spines of the Thread-rayed Brittle Star, which lives in 
soft slimy mud. Its third spine on the side of the joint is the 
largest, and instead of tapering to a point like the others, is 
furnished at its extremity with two transverse-curved spiny 
processes, giving it exactly the form of a pickaxe. Forbes 
considered that the arrangement would be useful in working 
about in the mud. 
The arms are readily cast off, in different places, in many 
species of Ophiurans, and often the disc alone may remain, the 
extremities wriggling for a while and dying, and the disc hoping 
to grow its arms again in time. Reparation is almost as certain 
as the mutilation. The Brittle Stars are extremely apt to break, 
and hence their very appropriate name ; but it appears that in 
perfectly comfortable circumstances one of them should and can 
carry its arms out of the battle-field of life safe and sound. 
Foul water, fright, what might be called in higher animals 
hysteria, and accident, produce breaking in bits, or the whole 
arm is cast, and the only way in which the process can occur, is 
by dislocating the system of pegs and sockets of the ossicles. 
Too great bending of the arm upwards, brings the lower peg 
out of its socket, and then there is a stress on the large upper 
one. The least excess of action of one set of side muscles 
over the other, will carry the ossicle out of its axial position, rup- 
ture the water system and nerves, and then the next motion of 
the joints nearer the body, will separate the structures. 
It is necessary, in conclusion, to notice the reproductive organs 
whose position is in the body around the stomach bag, and external 
to and above the water tube and nerve ring. On turning the 
Ophiuran on to its proper upper part, and then examining 
the body close to the arms within the disc, slits will be seen 
parallel with them ; in some genera there is one on each side 
of the arm on the body, and in others there are two, one 
