1917-] S. Kemp: Fauna of the Matlah River. 235 



The chief interest of this fauna, and the point with which this 

 note is mainly concerned, is the extraordinary resemblance which 

 the species bear to those inhabiting great depths of the sea. I am 

 convinced that if anyone with experience of both deep-sea and 

 shallow-water faunas were to have made a casual inspection of 

 the contents of the nets we hauled in the Matlah River, he would 

 have expressed the opinion that the catch came from water not 

 less than 400 fathoms in depth. On closer inspection he would 

 no doubt find reason to alter his opinion, for only one of the species 

 is a member of a deep-sea genus and few belong even to families 

 known from considerable depths. But in general facies the two 

 faunas resemble one another so closely that he would almost cer- 

 tainly be deceived at first sight. 



The bottom of the Matlah River, with its rapid currents and 

 moving silt, affords an environment altogether unsuitable for 

 sedentar}^ or slow moving organisms, and it is to this feature that 

 the predominance of Crustacea and fish must be ascribed. Con- 

 ditions in the deep sea are evidently difi'erent, for fixed animals 

 such as Hexactinellid sponges are often far from uncommon, while 

 creatures of slow movement such as the leather}^ sea-urchins and 

 Holothurians are often very abundant. It is in the fish and 

 Decapods that the peculiar character of the Matlah fauna is ex- 

 hibited and it is, moreover, in the most abundant species that the 

 resemblance to deep-sea forms is most pronounced. 



The modifications that give to the deep-sea fauna its peculiar 

 facies may be discussed under two headings, — form and colour; 

 and in view of what has already been said it will be sufficient to 

 refer here only to the fish and Decapod Crustacea. 



The colours of deep-sea fish are very limited. The great 

 majority of the species are deep black, grey of varying intensity, 

 silver, and semitranslucent or dead white. Two or more of these 

 colours are frequently found in combination. Reddish and brown- 

 ish tints are very rare and blues and yellows are almost non- 

 existent. In the Matlah fish there are no black forms, the ma- 

 jority being grey, white or silver. The Macrones is very deep grey 

 above and dull white below, with black fins ; the Pangasius, Setae- 

 na and Umbrina are grey and silvery and the Trichinrns and 

 Kurtus altogether silvery. Coilia dussmteri is white with a lateral 

 row of brilliant silver spots, while Harpodon nehereus is semitrans- 

 lucent milky white with minute black dots. An exception is 

 Polynenms paradiseus, which though greyish above has dull golden 

 brown sides. 



The range of colour in deep-sea Crustacea is even more limited 

 than in the case of fish. A considerable number of the species are 

 uniformly crimson, red or pink, while in a few cases purple tones 

 are found. Other species are ivory or milky white, frequently 

 semitranslucent, and these are sometimes blotched or streaked with 

 red, orange or yellow. Forms which are uniformly orange or yellow 

 also occur, but are less common. In the great majority of cases 

 the eggs are yellow or yellowish green. 



