Percomorphi 269 



a sword made of consolidated bones. The teeth are very feeble 

 and the ventral fins reduced to two or three rays. The species 

 are few in number, of large size, and very brilliant metallic 

 coloration, inhabiting the warm seas, moving northward in 

 summer. They are excellent as food, similar to the swordfish 

 in this as in many other respects. The species are not well 

 known, being too large for museum purposes, and no one having 

 critically studied them in the field. Istiophorus has the dorsal 

 fin very high, like a great sail, and undivided; Istiophorus ni- 

 gricans is rather common about the Florida Keys, where it 

 reaches a length of six feet. Its great sail, blue with black 

 spots, is a very striking object. Closely related to this is 

 Istiophorus orientalis of Japan and other less known species 

 of the East Indies. 



Tetrapturus, the spearfish, has the dorsal fin low and divided 

 into two parts. Its species are taken in most warm seas, 

 Tetrapturus imperator throughout the Atlantic, Tetrapturus am.'- 

 plus in Cuba, Tetrapturus mitsukurii and Tetrapturus mazara 

 in Japan. These much resemble swordfish in form and habits, 

 and they have been known to strike boats in the same way. 



Fossil Istiophoridce are known only from fragments of the 

 snout, in Europe and America, referred provisionally to Istio- 

 phorus. The genus Xiphiorhynchus ; fossil swordfishes from the 

 Eocene, known from the skull only, may be referred to this 

 family, as minute teeth are present in the jaws. Xiphiorhyn- 

 chus priscus is found in the London Eocene. 



The Swordfishes: Xiphiidae. The family of swordfishes, 

 Xiphiidce, consists of a single species, Xiphias gladius, of world- 



FIG. 211. Young Swordfish, Xiphias gladius (Linnaeus). (After Lutken.) 



wide distribution in the warm seas. The snout in the sword- 

 fish is still longer, more perfectly consolidated, and a still more 

 effective weapon of attack. The teeth are wholly wanting, 

 and there are no ventral fins, while the second of the two fins 

 on the back is reduced to a slight finlet. 



