298 A NATURALIST IN BORNEO 



on the mud or on the mangrove-roots, but as the tide 

 rose the crabs retired to their burrows, bearing in their 

 claws a lump of mud. This mud was used to plug 

 the mouth of the burrow, the crab backing into its 

 burrow and manipulating the mud from inside until 

 the opening was hermetically sealed. When the tide 

 fell again the mud plugs were pushed out and the 

 crabs emerged into the open once more. 



The great stretches of sand exposed at low tide just 

 beyond the mouths of the Sarawak River had a char- 

 acteristic fauna of their own. On one occasion, after 

 a heavy blow in the North-East Monsoon, I found the 

 shore strewn for at least two miles with thousands of 

 a peculiar gelatinous Holothurian with a smooth white 

 skin. Shoals of those queer little amphibious fish, the 

 Periophthalmi, were a very characteristic element in 

 this shore fauna. At low tide they were seen sunning 

 themselves in shallow pools, and at the least disturbance 

 would rush towards the sea, the flapping of their bodies 

 and tails against the wet sand making a noise like the 

 squattering of ducks in mud. As the eyes of these 

 fish are situated high on the top of the head they can 

 detect the approach of an enemy from any side very 

 readily, and as they are easily alarmed and can move 

 at a surprising pace, it is a matter of difficulty to catch 

 them. The only practicable way of getting large 

 numbers of specimens is to fire into the brown of a 

 shoal with small dust-shot. A species of Periophthalmus 

 closely allied to the shore-frequenting form is found 

 on river banks as far inland as the influence of the 

 tides is felt ; it occurred also at Kuching in ditches, 

 and lived in burrows well above low-water mark ; the 

 natives assert that this species is viviparous, but I 



