334 TRANSACTIONS, NATURAL HISTORY SOCIETY OF GLASGOW. 
the sand goes far to prove that they came up out of their burrows 
to die. I have noticed that those I have had in confinement do 
the same. , 
What I wish chiefly to bring forward just now with regard to 
this species is its habit of travelling under the sand—a habit that 
I am not aware of having been hitherto noticed. In following out 
some other experiments on the animal, I placed one of them in a 
glass vessel, covering it with sand, and allowing only the tips of 
the long dorsal spines to remain bare. Leaving it for the night, 
I found in the morning that it had travelled under the sand eleven 
inches, and its course could be traced by the track the tips of the 
spines had made on the surface. No attention was paid to the 
animal during the day, further than to observe that it was still in 
its burrow. Next morning the test was half-exposed above the 
sand, and the fine undulations that it had made on the surface 
showed that it had travelled considerably further above than it 
had done the night before underground. We may assume that 
the greater progress it had made on the surface was because of the 
less resistance it had to encounter. When we consider the broad 
front of the animal we will have some idea of the energy required 
to push its way through the stiff sand. We can scarcely believe 
that the progress they make under the sand is accomplished by 
mere pressure, but rather by the mining action of the spines. 
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