THE FISH OF THE DEEP SEA 149 



Raia hyperborea and Chimcera monstrosa, it is true, 

 just enter into the abysmal zone, but Chimcera affinis 

 is the only Elasmobranch that extends to depths of 

 over 1,000 fathoms. 



The Ganoidei too, the order that in palaeozoic 

 and mesozoic times was so rich in genera and species, 

 is entirely absent from the abysmal zone, not a single 

 representative having been found at any time by any 

 of the deep-sea expeditions. 



The Dipnoi, that remarkable order including the 

 three fresh-water genera, Ceratodus from Australia, 

 Lepidosiren from Brazil, and Protopterus from West 

 Africa, has no representative and no ally in the deep 

 waters of the ocean. 



The fishes of the deep sea, in fact, with only one 

 or two exceptions, all belong to the Order Teleostei, 

 the most modern and most highly differentiated order 

 of the class, the families that are most fully repre- 

 sented being the Macruridae and then the Ophidiidas 

 and Gadidas, and the Berycidse. 



At the limits of the katantic and abysmal zones, a 

 large number of families of Teleosteans entirely dis- 

 appear, and as we approach the deepest parts of the 



ocean, the number of fish that are found is consider- 



% 

 ably reduced. As Dr. Giinther very wisely remarks, 



