SOFT-RAYED BONY FISHES III 



Among other better known species are Trachypterus wis, from 

 the Mediterranean ; T. r ex-salmon or um, from the Pacific 

 coast of America ; and T. ishikawce, from Japan. 



The Deal-fishes are among the rarest of the inhabitants of 

 the open sea, and our very limited knowledge of these curious 

 creatures is derived almost entirely from the occasional 

 specimens found in a dead cr dying condition at the surface 

 or cast up on the beach after a storm. They have never been 

 taken in the trawl or in any other kind of deep-water net. So 

 fragile are their bodies that the individuals cast ashore are 

 almost invariably damaged, and as the tide recedes the carcase 

 shrivels up and almost disappears, both flesh and bones being 

 made up largely of water. We know, however, that as a 

 general rule fishes living in the upper layers of the sea have 

 large eyes and a silvery coloration, whilst those from the 

 deeper layers have small eyes and uniformly black bodies. 

 From this fact it may be inferred that the Deal-fishes are not 

 inhabitants of great depths, as is sometimes stated, but 

 probably live in water from the surface down to 200 or 300 

 fathoms. 



Nothing is known of their normal food or of their breeding 

 habits, but young Deal-fishes, 2 to 4 inches long, have been 

 captured from time to time, and in the case of the Mediterra- 

 nean species a nearly complete series of growth stages has been 

 seen. This reveals that the young fish are quite unlike their 

 parents, and that three or more stages have been erroneously 

 regarded by earlier writers as representing distinct species. 

 In the youngest stage known (about 16 mm. long) the front 

 rays of the dorsal fin, all those of the pelvics and those of the 

 lower lobe of the caudal fin are drawn out into fine streamer-like 

 filaments, which may be many times longer than the body 

 and are ornamented with lappet-like skinny processes. It may 

 be noted that in these very young fish the caudal fin is of the 

 normal type, but later on this becomes divided into a smaller 

 and quite rudimentary lower part and a larger upper one, 

 which projects obliquely or even vertically upwards. As 

 growth proceeds the filamentous fin-rays become progressively 

 shorter and the lower lobe of the tail disappears. It may be 

 assumed that the young Deal-fishes live at some considerable 

 depth, where the water would be reasonably still, as the 



