170 



FISH GALLERY. 



The Sword-fishes (Xiphiidae and Histiophoridae) are too large 

 to exhibit in the Wall-case among the families to which they 

 are most nearly related, and are placed in the special case 

 (24) that stands in the centre of the Gallery. The only 

 specimens representing these families in the Wall-case are three 

 vertebra; (742) from the tail region of a large Sail-fish (Histio- 

 phorus) showing how the caudal vertebrae interlock by means 

 of forwardly directed laminae of bone arising from the front of 

 the neural and haemal spines. A somewhat similar but less 



Fig. 80. — A Sword-fish, or Sail-fish, Histiophorus gladius. 



Sword- 

 fishes. 

 Floor- 

 case 24. 



pronounced interlocking occurs in the tail vertebrae of the 

 Mackerel (see 705, Wall-case 15). 



The Sword-fishes (Floor-case 24) are among the largest of 

 the Teleostean fishes, and may attain a length of fifteen feet. 

 They live in the open ocean, and are strong and rapid swimmers. 

 The Sword-fishes of the Indian and Pacific Oceans, sometimes 

 called Sail-fishes, belong to the genus Histiophorus (fig. 80), 

 and have long, narrow pelvic fins. The Sword-fishes of the 

 genus Xiphias are of world-wide distribution, and have no pelvic 

 fins ; they have transverse processes to the vertebrae and short 

 ribs, whereas Histiophorus has not. In the Histiophoridae there 

 is, at the front of the lower jaw, a supernumerary bone known 

 as the predentary bone ; this is wanting in Xiphias. The 

 " sword " or rostrum is formed by the prolongation of the 



