616 COXTRIBUTIOXS TO NORTH AMERICAN ICHTHYOLOGY IT. 
aa. Dorsal spines to 11. (Pomacaniliu^). 
96>>. P. arcuatus (L.) Lac. 
Dark brotrn. anteriorly iilain; lower javr pale : each scale with a daik 
.sjwt and a whitisli edge : young with yellowish vertical bauds, some- 
times spotted with black; base of pectorals sometimes yellow. Scales 
on body small, hrm: large and small ones irregularly mixed. Head with 
shagreen, formed of rudimentary scales. Dorsal and anal extremely 
falcate, the anterior soft rays two-thir.ls the length of the body in the 
adult; dorsal spines very low; last anal .spine long. Month small; 
gill-rakers short; gill-membranes very slightly joined to the isthmus 
mesially. D. IX. 30; A. Ill, 24; Lat. 1. 80-100; coeca 15; vert. 10-}- 
14. West Indies, north to Garden Key, Florida. 
{Chcpiodon arcuatm L. Svst. Nat.: Pomneanthus pani, cingulatus, quinquecincius, and 
arcuatus Cuv. A: Val. vii, 202-211: Pomaoanthus paru Gunther, iii, 55.) 
Family XCIX.-ACAXTHURID.E.* 
{The Surgeons.) 
Body oblong, compressed and usually elevated, covered with very 
small scales ; lateral line continuous. ' Tail armed with one or more 
movable spines or bony XJlates. Eye lateral, high up; j) reorbital very 
narrow and deep. Xo.strils double. Mouth small, low; each jaw with 
a single series of incLsor-like teeth; vomer and jtalatines toothless; pre- 
maxillaries .somewhat movable, bat not protractile; maxillary short; 
gill-rakers obsolete; p.seudobranchife large; gills 4, a slit behind the 
fourth; gill-membranes attached to the isthmus, the o])enings thus re- 
stricted to the sides. A single d ;r.sal fin, with strong .spines, the spi- 
nous part of the fin about as long as the soft part; anal fin similar, 
.shorter; ventral fins present, thoracic, mo.stly I, 5 (never I, 4, I, as in 
Tenth id (do^). Pelvic bone long, evident thi ongh the skin, as in Balistidce, 
with which group the Acanthuridee have numerous afiiuities. Pyloric 
coeca rather few. Air-bladder large. Herbivorous fishes of the tropicat 
seas; genera 5 or more; species nearly 80, most of them belonging to 
Acanthurus. 
{Acronuridae Gunther, iii, 356.) 
a. Tail -with a movahle lancet-like spine on each side; incisors serrate. 
Acaxthurus, 330. 
Called Teuthididcc in the key on page 78. 
