PELAGIC FAUNA 



79 



The new bathy pelagic sea-cucumber Galatheathuria, seen from above, from the side, 

 and from below. 



represented in the depths, though for the most part by other species, some 

 of remarkable appearance. But in certain groups of otherwise typical 

 bottom-dwellers there are also a few species which have adapted them- 

 selves to a free-swimming life. 



Of the sea-cucumbers a few live pelagically. A few bottom-dwellers are 

 able to ascend by wriggling up and down like leeches, but three forms are 

 specially adapted to a pelagic mode of life. The first of these was found 

 in 1 89 1 off the west coast of Central America, and given the name Pela- 

 gothuria natatrix (Fig. p. 76). It has since been taken in several localities 

 in the tropical parts of the Pacific and Indian Oceans. Only one species 

 is known. It attains a length of i o centimetres and has a small, thin-walled 

 body without the calcareous spicules characteristic of sea-cucumbers, and 

 a large swimming fringe which almost encloses the mouth — it swims 

 mouth upward. It is rose-coloured with a dark violet hind part. We found 

 it at a number of stations between Africa and Ceylon (as many as 41 

 specimens in one trawl), in the Bay of Bengal, in the Kermadec Trench, 

 and in the Gulf of Panama. The second genus is Enypniastes (formerly 

 called Planktothuria). This also lacks calcareous spicules in the skin. It 

 also has no swimming fringe, but remains buoyant by means of its very 

 thick, gelatinous body-wall. Two species had been known, both of which 

 we caught in the Bay of Bengal and, in considerable numbers, in the Great 

 Australian Bight. 



