GREGORY: FISH SKULLS 



317 



rostrum (Fig. 197) is braced especially by the broad anterior end of the vomer and by the 

 broad nasals. Tate Regan (190%) has traced the evolution of the rostrum in Histiophoridae, 

 Xiphiidae and related families from the beak-like premaxillse of Acanthocybium of the Scom- 

 bridae, while Starks (1910, p. 81) states that it was long ago pointed out that Acanthocybium 



e^iot 



B 



Istfophorus 



exo 



Fig. 197. Istiophorus. A. Under side. B. Top view. 



shows an apparent divergence toward the swordfishes. Scomberomorus shows the initial 

 step. Cybium Chinese of the Scombridae as figured by Kishinouye would indeed appear to 

 form an ideal structural ancestor for the marlins and sailfishes both in external characters 

 and skull structure (Plate I). 



Postscript. — The comparative study of the otoliths by G. Allan Frost (1927^, p. 302; 

 1928i, p. 328) shows that Tnchurus of the carangids has a sagitta resembling that of Perca, 



