1670 Bulletin 4.7, United States National Museum. 



smooth ; lateral line present, concurrent with the back, not extending on 

 the caudal fin; mouth small, protractile, terminal; maxillary very short, 

 irregular in form, divided in two by a longitudinal suture ; upper part of 

 skull solid, occipital crest strong; post-temporal firmly joined to the 

 skull, its form really trifurcate though appearing simple, the interspaces 

 between the forks filled in by bone so that only a foramen is left; last 

 bone of suborbital ring firmly joined to the preoperculum ; teeth brush- 

 like or setiform, often extremely long, in narrow bands in the jaws; no 

 teeth on vomer or palatines; no canines, molars, or incisors; eyes lateral, 

 of moderate size; branchiostegals 6 or 7; pseudobranchise very large; air 

 bladder present. Gill membranes more or less attached to the isthmus; 

 gill rakers very small. Dorsal fin single, continuous, its rays sometimes 

 filamentous, its soft part as well as the soft part of the anal densely cov- 

 ered with small scales ; anal similar to the soft dorsal with 3 or 4 spines ; 

 ventrals thoracic, I, 5 ; caudal usually truncate. Vertebrae 10 -f- 14 = 24, the 

 anterior abbreviated; insertion of the ribs inferior; post-temporal usually 

 reduced, and not bifurcate. Carnivorous fishes of the tropical seas, noted 

 for their singular forms, bright colors, and great activity. Genera 8 to 10 ; 

 species about 180, most of them belonging to Chcvtodon and Pomacanthus. 

 The excessive quickness of sense and motion enable these fishes to main- 

 tain themselves in the struggle for existence in the close competition of 

 the coral reefs notwithstanding their bright colors. The young are very 

 different from the adult, and pass through a stage termed Tholichthys in 

 which the membranes are greatly developed, forming collars and sheaths 

 about head and neck. (Squamipinnes, part, Gunther, Cat., n, 1-57, 1860.) 



a. Preopercle unarmed ; dorsal spines not graduated, some of the median spines longer 

 than the last spines; scales comparatively large (young with the Tholichthys 

 form). 



b. Snout (nasals, palatines, etc.) with premaxillaries, articular, and dentary bones 

 much produced, beak-like; cleft of mouth, with maxillaries, short; lateral line 

 ceasing under soft dorsal. 

 c. Dorsal spines 12 or 13 ; soft rays about 20 (19 to 23). 



d. Scales large ; beak moderate. PROGNATHODES, 657. 



dd. Scales small, about 75 in horizontal series ; beak very long. 



FORCIPIGER, 658. 



bb. Snout little if at all produced; dorsal spines usually 12 to 14; not graduated, 

 some of the middle ones highest ; anal spines 3. CH^TODON, 659. 



POMACANTHINJE : 



aa. Preopercle armed at its angle with a very strong spine, which is sometimes grooved. 



e. Interopercle unarmed; vertical limb of preopercle above spine entire or nearly 



so ; dorsal fin with 8 to 11 spines, its soft rays 23 to 32. POMACANTHUS, 660. 



ee. Interopercle short and broad, armed with 1 to 4 strong spines; preopercle ser- 



rate or spinous ; dorsal spines about 14, graduated, the last one longest ; 



scales rather small ; isthmus very narrow. 



/. Vertical limb of preopercle simply serrate, with 10 to 30 small teeth ; body 



oblong, rather robust. HOLACANTHUS, 661. 



/. Vertical limb of preopercle with 3 to 9 conspicuous spines ; body ovate, 



much compressed. ANGELICHTHYS, 662. 



