DISTRIBUTION 127 



amphipods and Tanaidacea are quite well represented. The isopods 

 in particular seem to have a number of species confined to this 

 region; Macrostylis galatheae is the deepest recorded species, being 

 found at a depth of 9,790 metres in the Philippine Trench. The only 

 crustacean known from deeper water is an unidentified amphipod 

 from 10,190 metres. 1 Decapods have not been found in the hadal 

 region, but some ostracods, a barnacle, mysids and a cumacean have 

 been dredged up from the various trenches of the Pacific. 



Fig. 57. Thaumastocheles zaleucus (Astacura). A blind 



deep sea decapod, from a depth of over 800 metres off the 



West Indies. Actual length of body about 10 cm. (After 



Spence-Bate). 



Too little is known about the distribution of the deep-water 

 Crustacea to make any definite assertions. It seems probable that 

 most of the abyssal genera are cosmopolitan where the oceans are 

 deep enough, but the species are more restricted in their distribu- 



1 Since this account was written both amphipods and isopods have been recorded 

 from 10,687 metres in the Tonga Trench. 



