GREGORY: FISH SKULLS 



405 



The skull is very broad, with widened vomers and triradiate frontals. Parietals are retained 

 as in the Oneirodidae. The elongate, many-rayed dorsal of Melanocetus polyactis (Fig. 272) 

 might at first sight be deemed more primitive than the short six-rayed dorsal of Dolopichthys 

 luetkeni; but it seems far more probable that the increas£ in the number of the dorsal fin- 



Do/opichrhys luetkeni 

 Fig. 277. Divergent Evolution in Ceratioids. Figures from Tate Regan. 



rays is quite secondary and that by creating a downward and forward thrust on the column 

 this long fin serves to redress the balance of the fish, which, with its enormously deep jaws 

 and upwardly slanting column, would otherwise find it difficult to move forward rather 

 than downward. 



