SWOED-FISHES. 431 



and the small eye leads one to suppose that these fishes live 

 in muddy water near the mouths of large rivers. The air- 

 bladder has been described on p. 144. 



Other genera belonging to this family are Larimus, Eques, 

 Nebris, and Lonchurus. 



Sixth Division — Acanthopterygii Xiphiifoemes. 



The upper jcav is produced into a long cuneiforyn weapon. 



These fishes form one small family only, Xiphiidce. 



The " Sword-fishes " are pelagic fishes, occurring in all 

 tropical and sub-tropical seas. Generally found in the open 

 ocean, always vigilant, and endowed with extraordinary 

 strength and velocity, they are but rarely captured, and still 

 more rarely preserved. The species found in the Indian and 

 Pacific Oceans belong to the genus Histiophorus, distinguished 

 from the common Mediterranean Sword-fish, or Xiphias, by 



Fig. 191. — Histiophorus pulchellus. 



the presence of ventral fins, which, however, are reduced to 

 two long styliform appendages. The distinction of the 

 species is beset with great difficulties, owing to the circum- 

 stance that but few examples exist in museums, and further, 

 because the form of the dorsal fin, the length of the ventrals, 

 the shape and length of the sword, appear to change accord- 

 ing to the age of the individuals. Some specimens or species 

 have only the anterior dorsal rays elevated, the remainder of 



