434 



TELEOSTEI 



number. The head is more or less completely covered with the scale- 

 bearing skin. Among the Chaetodontiformes are some of the most 

 specialised of Teleostean fish ; they diverge 

 greatly from the Perciform stock from which 

 they appear to have arisen. 



DIVISION A. SQUAMMIPENNES. These still 

 preserve many of the primitive characters : 

 there are a subocular shelf, ctenoid scales, 

 four gills, paired and median fins with spines, 

 and well -developed pleural ribs. The body- 

 scales extend between or over the dermal rays 

 of the median fins. They are probably more 

 closely related to Sub-Tribe B than to any 

 other Perciformes. 



Family CHAETODONTIDAE. The body 

 becomes very compressed and deep, the mouth 

 produced forward, the 'face' more vertical, 

 and a very high supraoccipital crest is con- 

 tinued at the sides into the pterotic crest ; 

 it is enormously enlarged in Ephippus (Fig. 

 442) ; the minute setiform teeth are set in 

 bands. The opercular bones may be armed 

 with spines ; in Holocanthus there is a pro- 

 minent preopercular spine. 



Chaetodon, Art. (Fig. 443) ; Holacanthus, 

 Lac. ; Pomacanthus, Lac. ; Ephippus, Cuv. ; 



Platax, C. and V. (Fig. 444) tropical seas ; Eocene, Europe. Chelmo, 



Cuv. ; Parapsettus, Stnd. 



FIG. 442. 



Skull of Ephippus fabcr, Br. 

 , enlargement of frontal, and 6, 

 />f supraoccipital ; c, interorbital 

 septum ; <?, basis cranii. (After 

 Giinther.) 



FIG. 443. 

 Chaetodon ephippium, C. and V. (After Giinther.) 



Family DREPANIDAE. Very like the last, but having lost the sub- 

 ocular shelf, and with very long specialised pectoral fins. 

 Drepane, C. and V. ; Indian Ocean. 



