FASCICULI MALATENSES 
299 
slanting, and lies in an oval or circular pool of water, which is retained round 
it as the tide sinks — for it is always made between tide-marks — by a rampart 
of mud some four to six inches in height, and about a foot-and-a-half in 
diameter. It is surrounded, outside the rampart, by a number of simple 
holes, which probably lead into the central shaft, though, owing to the liquid 
condition of the mud, we were unable to demonstrate this by digging. When 
thoroughly alarmed, the fish sometimes enters one of these holes, but if only 
a little scared, it rushes to the rampart, surmounts it, and sits for a longer or 
shorter period on it before diving into the pool and disappearing. It seemed 
quite evident to us that each individual had its proper burrow, but how many 
inhabited one burrow we could not ascertain ; it appeared that their number 
must be small. The central pool was always entered at one point, so that a 
definite furrow was made on the rampart, and the characteristic tracks of the 
fish — consisting of a central line (made by the tail) and two series, running 
parallel to one another on either side of the line, of more or less hand-shaped 
depressions (made by the tips of the more prominent pelvic rays and the web 
between them) — converged towards it, showing readily whether the fish had 
recently gone out or in. 
At first we were much puzzled as to how the rampart and burrow were 
made, but the natives told us that the fish wriggled down into the mud? 
filled its mouth with the stiffer clay beneath the surface, and built up the 
wall with pellets thus brought from below. We found it impossible to 
confirm their statement by actual observation, but there is every reason, in 
this case, to regard them as accurate observers, for the colour of the walls 
plainly showed that they were not made of surface mud, while the shape and 
size of the pellets, which could easily be distinguished in freshly constructed 
specimens, were just what would have been expected had they been casts of 
the inside of the mouth of an adult of P. phya ; nor did we ever see a small 
specimen enter one of the burrows. One of us watched a large individual 
repairing its rampart, which had been injured by the tide, for some time, but 
could not be sure exactly how this was accomplished ; the fish certainly went 
down the central hole and returned in a few seconds, bringing a pellet of mud 
with it. 
The eyesight of this species appears to be keen, both in air and water, 
and to range in the former element for a radius of at least thirty feet. We 
noticed repeatedly that when we had frightened an individual into its burrow, 
it remained concealed as long as we stayed still, but reappeared as soon as we 
began to move away ; and this would seem to indicate that the fish could see 
from beneath the surface of the water what was going on in the air. On 
