Genera of Acanthuridae — Randall 365 
leucosternon Bennett or A. nubilus , A. bleekeri 
Gunther, and A. thompsoni (Fowler); however, 
I do not believe that even these are advisable. 
The late postlarval Acanthurus is quite dif- 
ferent from the juvenile. It is more disc-like, 
transparent in life with silvery abdomen, and 
naked with vertical striae or folds on the 
body. It is not difficult to understand why 
Gronow erected Acronurus for this stage and 
how this genus persisted so long in the litera- 
ture. Although now well known to be larval, 
acronurus remains as a common name for the 
late postlarval stage of Acanthurus . Some au- 
thors apply the designation to all postlarval 
acanthurids. 
The type species of Acronurus by subse- 
quent designation is Acanthurus argenteus 
Quoy and Gaimard. As indicated by Randall 
(in press), this species may be the young of 
Ctenochaetus striatus (Quoy and Gaimard). If 
this could be conclusively demonstrated, the 
generic name Ctenochaetus would have to be 
replaced by Acronurus. Under such circum- 
stances, it would be advisable to apply to the 
International Commission on Zoological No- 
menclature to conserve the name Ctenochaetus. 
Nearly all use of Acronurus has been for the 
young of Acanthurus. 
Swainson (1839) listed Teuthys as a surgeon 
fish genus (an emendation or erroneous spell- 
ing for Teuthis Linnaeus) for the single species 
Acanthurus argenteus Quoy and Gaimard. His 
brief description of the genus obviously ap- 
plies to an acronurus. Linnaeus, however, did 
not include any acronurus forms in Teuthis. 
Seale placed in Zabrasoma (probably a typo- 
graphical error for Zebrasoma) , his new species 
agaha (= flavescens ) and a species of Acan- 
thurus (A. guttatus). He apparently mistook 
A. guttatus for a Zebrasoma because of its high 
body. 
Genus Ctenochaetus Gill 
Ctenodon Klunzinger, 1871. Synopsis Fische 
Rothen Meeres. Pt. 2, p. 509. (Preoccupied 
by Ctenodon Wagler, 1830.) 
Ctenochaetus Gill, 1885. U. S. Natl. Mus., Proc. 
7: 279. (Type species by original designa- 
tion, Acanthurus strigosus Bennett.) 
Ctenodon was first proposed by Wagler 
(1830) for a reptile. Swainson (1839) used the 
same generic name for five species of Acan- 
thurus and one Ctenochaetus. Klunzinger ap- 
plied the name as a subgenus for the species 
Acanthurus ctenodon Cuvier and Valenciennes 
( = Acanthurus striatus Quoy and Gaimard) 
and Acanthurus strigosus Bennett. Fowler (1904: 
545) elevated Klunzinger’s subgenus to a 
genus. 
The use by Day (1889: 143) (and subse- 
quent authors) of Acanthurus for Ctenochaetus 
(and Teuthis for Ctenochaetus by Barnard, 1927: 
780) appears to be due to ignorance of Gill’s 
name Ctenochaetus for this well- differentiated 
genus. 
As is indicated in the discussion of Acro- 
nurus in the section on Acanthurus there is 
a possible question as to the validity of the 
name Ctenochaetus. 
SUPPLEMENTAL NOTE 
After the present paper was submitted, an 
article by Prof. J. L. B. Smith, entitled East 
African Unicorn Fishes from Mozambique , ap- 
peared in the South African Journal of Science 
(65 (6): 169-174). Five genera (here considered 
only as the single genus Naso ) and Prionurus 
were split off from the Acanthuridae on the 
basis of caudal armature and placed in a sep- 
arate family, the Nasidae. 
If only the genera Naso and Acanthurus were 
considered, such a division would be tenable. 
It is not, however, when all of the genera are 
considered. Par acanthurus has the single folding 
caudal spine, strongly denticulate teeth, IX 
dorsal and III anal spines like Acanthurus, but 
I, 3 pelvic rays and thickened dorsal spines like 
Naso. Prionurus, linked with Naso by Smith 
because of the three to six fixed caudal spines 
or laminae on each side of the caudal peduncle, 
has a pelvic formula of I, 5, VIII or IX dorsal 
and III anal spines, and dentition similar to 
Acanthurus. Zebrasoma would seem to be allied 
with Acanthurus in caudal armature and other 
characters, yet it has a reduced dorsal spine 
count like Naso. 
Smith divides Naso as here defined into the 
five genera Axinurus, Naso, Cyphomycter, Calli- 
