668 TELEOSTEI 



An Atlantic species of Ephippus (E. faber) is extremely 

 remarkable, when adult, for an enormously enlarged globular 

 bony mass on the back of the head, formed by hypertrophy of the 

 frontal and supraoccipital bones. 



Principal genera : Epliippus, Parapsettus, Scatophagus, C/iae- 

 todon, Chelmo, Heniochus, Holacantlms, Pomacantkus, Platax. 



Chaetodon, Holacanthus, Pomacanthus, Scatophagus, Ephippus, 

 and Platax were represented in the Eocene of Europe. 



Fam. 28. Drepanidae. The genus Drepane, with a single 

 species from the Indian Ocean, is very closely related to the 

 Chaetodontidae, but it lacks the subocular shelf, and it is distin- 

 guished externally by the very elongate, falciform pectoral fin. 



Fam. 29. Acanthuridae. A more or less developed sub- 

 ocular shelf; entopterygoid present. Mouth very small, not or 

 but slightly protractile, the maxillary more or less firmly attached 

 or ankylosed to the praemaxillary ; teeth conical, bristle-like, or 

 incisor-like. Palate toothless. Vertebrae 22 or 23, the prae- 

 caudals with strong transverse processes commencing from the 

 first ; ribs and epipleurals inserted on the transverse processes. 

 Post-temporal not distinctly forked, ankylosed to the skull. Two 

 nostrils on each side. Gill-membranes broadly attached to the 

 isthmus ; 4 or 5 branchiostegal rays ; gills 4, a slit behind 

 the fourth ; pseudobranchiae present. Lower pharyngeal bones 

 separate. Body covered with minute, often rough scales. Dorsal 

 and anal fins elongate, with more or less strong spines. Ventrals 

 with 1 spine and 2 to 5 soft rays. 



A family of about 80 species, mostly herbivorous, from the 

 tropical seas, referred to 6 genera : Zanclus, Ctenochaetus, Acan- 

 thurus, Colocopus, Prionurus, Naseus. They form a connecting 

 link between the Chaetodontidae and the Plectognathi. 



Eemains from the Eocene of Europe have been referred to 

 Zanclus, Acantkurus, and Naseus, and to the extinct genera 

 Aulorliamplius and Apostasis. 



Fam. 30. Teuthididae. No subocular shelf; entopterygoid 

 present. Mouth very small, beak-like, not protractile, with 

 incisor-like teeth ; maxillary ankylosed to the praemaxillary. 

 Palate toothless. Two nostrils on each side. Gill-membranes 

 broadly attached to the isthmus ; 5 branchiostegal rays ; gills 

 4, a slit behind the fourth ; pseudobranchiae present. Lower 

 pharyngeal bones separate. Supratemporal forked. Vertebrae 



