362 - 
BULLETIN OF THE UNITED STATES FISH COMMISSION. 
distal end only of upper limb attached. The supra-clavicle short and triangular, bearing a short spine 
near its anterior angle, its posterior edge divided into 3 spines, 2 or 3 of which stand out above the 
surface of the skin. Ventral edge often serrate, with strong bony plates; lateral line well developed, 
concurrent with the back; branchiostegals 7 or 8; gill-openings wide, the membranes little united, 
free from the isthmus; psfeudobranchise large; air bladder large; gillrakers usually short; gills 4, a 
slit behind the fourth; dorsal tin emarginate or divided, the anterior part with spines, which are often 
strong, the posterior part longer, its highest rays behind the middle; soft anal entirely similar to soft 
dorsal, usually preceded by 1 to 4 spines, which are not graduated and which often form a separate 
tin; ventral tins thoracic, well developed, their rays usually i, 6 to i, 8; pectorals small; caudal fin 
rounded, on a moderate peduncle. Lateral line obscure, unarmed. Pyloric caeca exceedingly numerous. 
Vertebrae about 32 (Zeus). Genera 8; species about 15; fishes of singular appearance, inhabiting warm 
seas, often at considerable depth. The species undergo great changes in the course of development. 
The single Hawaiian genus and species is fully described in Section II. 
Family LXXIII. CH^TODONTIDtE.— Butterfly-Fishes. 
Body' strongly compressed, elevated, suborbicular in outline, covered with moderate-sized or small 
scales, which are finely ciliated or nearly 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 2 by a longitudinal suture; upper part of skull solid, occipital crest strong; post-tem- 
poral firmly joined to the skull, its form really trifurcate, though appearing simple, the spaces between 
the forks filled in by bone so that only a foramen is left; last bone of the suborbital ring firmly joined 
to the preopercle; teeth brush-like orsetiform, often extremely long, in narrow bands on the jaws; no 
teeth on vomer or palatines; no canines, molars or incisors; eyes lateral, of moderate size; branchi- 
ostegals 6 or 7; pseudobranchiae very large; air-bladder present; gill-membranes more or less attached 
to the isthmus; gillrakers very small; dorsal fin single, continuous, its rays sometimes filamentous, its 
soft part as well as the soft part of anal densely covered with small scales; anal similar to soft dorsal 
with 3 or 4 spines; centrals thoracic, I, 5; caudal usually truncate; vertebrae 10-fl4=24, the anterior 
abbreviated; insertion of ribs inferior; post- temporal usually reduced, and not bifurcate. 
Carnivorous fishes of the tropical seas, noted for their bright colors and great activity. Their exces- 
sive quickness of sense and motion enables them 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 Tholichthys, in which the membranes are 
greatly developed, forming collars and sheaths about the head and neck. 
Chxtodontinse: 
a. Preopercle unarmed ; scales comparatively large (.young with the Tholichthys form). 
b. Snout (nasals, palatines, etc.) with premaxillaries, articular, and dentary bones much produced, very long, beak- 
like; scales small, about 75 in horizontal series; dorsal spines 2 Forcipiger, p. 362 
bb. Snout little, if at all, produced; scales larger, about 35 to 60. 
c. Dorsal fin with none of the spines elevated or filiform. 
d. Scales large, usually 35. to 50 in lateral line; dorsal spines 12 to 14; teeth moderate Chsetodon , p. 363 
dd. Scales rather small, about 60 in lateral line; dorsal spines 10 or 12 Microcanthus, p. 376 
cc. Dorsal fin with the fourth spine much elevated and filiform Heniochus, p. 376 
Poinocanthinse: 
aa. Preopercle armed at its angle with a very strong spine, which is sometimes grooved; preopercle serrate or spinous, 
with 10 to 30 small teeth; dorsal spines about 14, graduated, the last one longest Holacanthus, p. 377 
Genus 173. FORCIPIGER Jordan & McGregor. 
This genus differs from Prognathodes Gill in having smaller scales, about 75 in a lateral series instead 
of 40. Chehno Cuvier is also closely related, having the same forceps-like mouth; but in the latter 
genus the spinous dorsal is much less developed, containing about 9 spines. 
Forcipiger Jordan & McGregor, Rept. U. S. Fish Comm., xxiv, 1898, 279 ( Chelmo longirostris Cuvier & Valenciennes). 
