248 
BULLETIN OF THE UNITED STATES FISH COMMISSION. 
pseudobran chise very large; air-bladder present. Gill-membranes more or less attached to isthmus; 
gillrakers very small. Dorsal fin single, continuous, its rays sometimes filamentous, its soft part as 
well as soft part of anal densely covered with small scales; anal similar to soft dorsal, with 3 or 4 spines; 
ventrals thoracic, i, 5; caudal usually truncate. Vertebrae 10 -f- 14 = 24, the anterior abbreviated; 
insertion of 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. The family comprises 8 to 10 genera and about 180 species, most of them belonging to 
Chsetodon and Pomacanthus. Their excessive quickness of sense and motion enables these fishes to 
maintain themselves in the struggle for existence in the close competition of the coral reefs, notwith- 
standing their bright colors. The young are very different from the adult, and pass through a stage 
termed Tholichtliys, in which the membranes are greatly developed, forming collars and sheaths about 
head and neck. 
Cioetodontin/E: 
a. Preopercle unarmed; dorsal spines not graduated, some of median spines longer than last spines; scales compara- 
tively large (young with the Tholiclithys form). 
b. Snout (nasal, 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 
bb. Snout little if at all produced; dorsal spines usually 12 to 14, not graduated, some of middle ones highest; anal 
spines 3 Ch^todon, 113 
Pomacanthin/E: 
aa. Preopercle armed at its angle with a very strong spine, which is sometimes grooved. 
c. 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, 114 
ec. Interopercle short and broad, armed with 1 to 4 strong spines; preopercle serrate or spinous; dorsal spines about 14, 
graduated, 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, 115 
ff. Vertical limb of preopercle with 3 to 9 conspicuous spines; body ovate, much compressed Angelichthys, 116 
Genus 113. CHIETODON (Artedi) Linnaeus. 
Body short, deep, very strongly compressed, especially above and behind; head small, compressed, 
almost everywhere scaly'; mouth very small, terminal, jaws provided with long, slender, flexible, 
bristle-like teeth; vomer sometimes with teeth; preoperculum entire or nearly so, without spine. 
Dorsal fin single, continuous, not notched, spinous part longer than soft part, of about 13 spines, spines 
not graduated, some of middle ones being longer than the last; last rays of soft dorsal usually rapidly 
shortened, some of them occasionally filamentous (in East Indian species) ; caudal peduncle short, 
caudal fin fan-shaped ; anal similar to soft dorsal, preceded by 3 strong spines. Body covered with 
rather large ctenoid scales, somewhat irregular in their arrangement; lateral line curved, high, parallel 
with back. Gill-openings rather narrow, membranes narrowly joined to isthmus; branchiostegals 6. 
A very large genus of singular and beautiful fishes, abounding in the tropical seas, especially about 
volcanic rocks and coral reefs; most of them have the body crossed by transverse black bars. They 
are all very active, feeding on small animals. 
a. Scales on trunk all subequal, their posterior margins regularly rounded. None of the rays of soft dorsal produced. 
Chauodontops: 
b. Series of scales below axis of body running obliquely upward and backward, lowest becoming more or less 
horizontal. 
c. Base of soft dorsal with a large black spot, not ocellated oceUatns 
d. Humeral band absent. 
e. Body with a dark band between dorsal and anal; no caudal ocellus. 
/. Ocular band edged with yellowish or whitish above; soft dorsal and anal with much black sedeniarius 
ff. Ocular band jet-black, not white-edged; soft dorsal and anal without black aya 
ee. Body without black crossbands, ocular band only present; an ocellus on caudal peduncle atxniatus 
CH.ETODON: 
bb. Series of scales below axis of body extending downward and backward, forming an angle with those above, each 
series marked by a continuous black streak. 
g. Body without ocelli, crossed by dark bands striatus, 205 
gg. Body with a large black ocellus below soft dorsal capistratua, 206 
ggg. Body with 2 ocelli, a large one on caudal peduncle and a smaller one on first 8 or 9 soft rays of dorsal... bricei, 207 
