350 REPORT OF NEW JERSEY STATE MUSEUM. 
ent, concurrent with back and not extending on caudal fin. 
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 III or IV spines. Ven- 
trals thoracic, I, 5. Caudal usually truncate. 
Carnivorous fishes of the tropical seas, noted for their singular 
forms, brilliant colors and activity. The excessive quickness of 
sense and motion enable these fishes to maintain 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 Tho- 
lichthys, 11 which the membranes are greatly developed, forming 
collars and sheaths about the head and neck. Several species 
straying to our shores. 
Key to the genera. 
a. CHETODONTIN#. Preopercle unarmed. CH ®TODON 
aa. POMACANTHIN#. Preopercle armed at its angle with a very strong spine. 
b. Interopercle unarmed; vertical limb of preopercle above spine, entire 
or nearly so; D. VIII to XI, 23 to 32. POMACANTHUS 
bb. Interopercle short and broad, armed with I to 4 strong spines; pre- 
opercle serrate or spinous; vertical limb of preopercile with 3 to 9 
conspicuous spines; D. about XIV, graduated, last spine longest; 
body ovate, much compressed. ANGELICHTHYS 
Genus CHATODON Linnzus. 
The Butterfly Fishes. 
Key to the species. 
a. Series of scales below axis of body running obliquely upward and back- 
ward, lowest becoming more or less horizontal; base of dorsal with a 
large black non-ocellated spot. OCELLATUS 
aa. Series of scales below axis of body running downward and backward, 
forming an angle with those above, and each series marked by a con- 
tinuous black streak; body without ocelli. STRIATUS 
Cheetodon ocellatus Bloch. 
PLATE 72. 
Head 2%4; depth 2%; D. XII, 18; A. III, 18; scales about 38 
to base of caudal, several more on latter; 45 pores in lateral line; 
g scales between origin of spinous dorsal and lateral line; 22 
scales between highest convexity of lateral line and origin of anal 
