350 REPORT OF XEW 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. x\nal 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 ^-ery 

 different from the adult, and pass through a stage termed Tho- 

 lichthys, in 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. Ch.^todontin.^. Preopercle unarmed. ch.i;todox 



aa. PoMACANTHiN.^. Preopeixle 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 2^. pomacanthus 



bh. Interopercle short and broad, armed with i to 4 strong spines ; pre- 

 opercle serrate or spinous ; vertical limb of preopercle with 3 to 9 

 conspicuous spines ; D. about XIV, graduated, last spine longest ; 

 body ovate, much compressed. axgelichthys 



Genus Ch.^todon Linnaeus. 

 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 



Chaetodon ocellatus Bloch. 



Plate 72. 



Head 2^ ; depth 2% ; D. XII, 18; A. Ill, 18; scales about 38 



to base of caudal, several more on latter ; 45 pores in lateral line ; 



9 scales between origin of spinous dorsal and lateral line; 22 



scales between highest convexity of lateral line and origin of anal 



