68o 



TELEOSTEI 



seas. Four or five species are distinguishable, and are referable 

 to two genera : JUistiophorus, with a single dorsal fin and 2 or 3 

 ventral rays, and Tetrapturus, with the dorsal divided into two 

 parts and a single ventral ray.^ 



Fossil Histiophoridae are known from the Eocene and later 

 beds in Europe and America. Dr. A. S. Woodward observes that 

 the known fossils are too imperfect to be referred with certainty 

 to their respective genera. Most of them probably belong to 

 Histiophorns, but at least one genus from the Eocene (JCiphio- 

 rhynchus) appears to be well distinguished. 



-^f^'^X^'^^^'^i^f^^i^n^^^^^ 



Fig. 416. — Tetrapturus helone, from the Mediterranean. (After Cuvier and 

 Valenciennes.) a y\j. 



The imperfectly known extinct family Palaeorhynchidae, from 

 the seas of the Eocene, Oligocene, and Miocene periods, with the 

 genera Palaeorhynehus and Hemirhynchus, is probably closely 

 related to the Histiophoridae. The vertebrae number 50 to 60, 

 and the ribs completely encircle the body. In Palaeorhynehus 

 both jaws are equally produced into an ensiform weapon. 

 Mochius, from the Eocene, with diamond-shaped, slightly over- 

 lapping bony scutes on the body, is perhaps also to be placed 

 near this family. 



^ For a detailed account of these fishes and of Xiphias, cf. Brown Goode, Proc. 

 U.S. Mus. iv. 1881, p. 415, and A'q). U.S. Fish Comm. f. ISSO. 1883, p. 289. 



