XXIII ACANTHOPTERYGII 715 
Fam. 1. Trachypteridae——Mouth very protractile; ventral 
fins more or less developed, with 6 to 9 rays, or reduced to a 
single long ray; no anal fin; vent about the middle of the body ; 
caudal rays, if present, divided into two fascicles, the upper some- 
times much prolonged and directed upwards. 
Fic. 432.—Trachypterus iris. <1. (After Cuvier and Valenciennes. ) 
Two genera. The most generalised is 7rachypterus, of which 
probably only 10 forms are entitled to specific distinction. The 
best known species is 7. arcticus, the Deal-Fish or Northern 
Ribbon-Fish, which reaches a length of 8 feet or more, and of 
which a few specimens have been stranded on the coasts of 
Scotland. Nilsson, who has observed these fishes alive on the 
Scandinavian coast, says they approach the shore at flood-tide on 
sandy shelving bottoms, and are often left by the retreating 
waves; that they move with one side turned obliquely upward, 
and that they lie on the side like Flat-Fishes on the bottom in 
2 or 3 fathoms of water. Regalecus' differs in the presence of a 
single ray to the ventral and the absence of the caudal fin. 
Some 5 or 6 species may be distinguished. . glesne, the Oar- 
fish, or “ King of the Herrings,” is the best known and the 
largest species, reaching a length of over 20 feet. About 25 
