GREGORY: FISH SKULLS 



279 



Chiztodon. — This fish (Fig. 155) has a minute protrusile mouth with bristle-lilce teeth, 

 a long lower jaw and moderately ascending processes of the premaxillae. The head and 

 body are vertically deepened so that the quadrate-articular fulcrum is brought far below 

 the mouth; thus its protrusility is increased. The opercular elements share in the general 



Chaetodon ocellatus 



Fig. 155. Chatoiion ocellatus. 



deepening. The extremely high supraoccipital crest is concurrent with the crest on the 

 pterotic. This feature is also conspicuous in other related families. The posttemporal is 

 closely ankylosed with the skull and the supracleithrum is nearly vertical. The eye is 

 large and the fish very alert, quick and even aggressive. 



Balistoidei (Acanthurids, Zanclids, Siganids, Teuthids, Plectognaths) 

 According to Boulenger (1910, p. 668), the surgeon-fishes (Acanthuridse) (Figs. 156, 

 157) and their allies "form a connecting link between the Chaetodontidae and the Plecto- 

 gnathi." Starks (1926fl, p. 277) from his studies of the ethmoid region judged that 



