328 
The genus Labroides is distinguished from 
other genera of the Labridae in having a small 
mouth with thick lips, the upper with a shal- 
low median groove and the lower divided 
into two prominent, anteriorly projecting 
lobes. The inner surface of the lips has fleshy 
folds. There is a single pair of large, curved, 
canine teeth anteriorly in each jaw, the upper 
pair fitting inside the widely-spaced lower 
pair when the mouth is closed. There is a 
large, anteriorly directed, canine tooth at the 
extreme posterior part of the upper jaw, sep- 
arated by a gap from anterior teeth. The 
remaining teeth are small, those in the lower 
jaw in several close-set rows between the ca- 
nines and those in the upper jaw forming a 
large mass just behind the anterior canines, 
this mass with a marked indentation anteri- 
orly in the mid-line. The body is compressed, 
its width contained about 2.5 to 3 times in 
the head length, and moderately elongate, its 
depth contained about 3.5 to 4 times in the 
standard length. The caudal fin is truncate or 
slightly rounded. The preopercle is entire, its 
margin smooth. The gill membranes are at- 
tached to the isthmus. The snout is pointed. 
The snout, entire dorsal surface of the head, 
chin, and throat are scaleless. The lateral line 
is continuous, and the lateral line scales num- 
ber 28 or 52 to 54. Fin ray counts are as fol- 
lows: D IX, 11 or 12; A III, 10; P 13 (upper- 
most two rays unbranched). The species are 
small, individual fish usually being less than 
100 mm. in standard length. 
KEY TO THE SPECIES OF LABROIDES 
(Applicable primarily to adults; 
see discussion below concerning juveniles) 
la. Lateral line scales 52 to 54; color light 
blue with a median lateral black band 
from snout to end of caudal fin (this band 
broadening as it passes posteriorly on 
body) (Indo-Pacific) 
Labroides dimidiatus 
lb. Lateral line scales 28; color not as above 
(although a median lateral black band is 
PACIFIC SCIENCE, Vol. XII, October, 1958 
often distinct anteriorly on body and on 
head) 2 
2a. Snout long, diameter of eye contained 2.1 
to 2.5 times in snout length; caudal pe- 
duncle and caudal fin pale with a promi- 
nent black crescent posteriorly in fin, the 
attenuate ends of which extend to mar- 
gins of caudal peduncle (tropical Pacific) 
Labroides bicolor 
2b. Snout not long, diameter of eye contained 
1.5 to 1.9 times in snout length; caudal 
peduncle and caudal fin black with upper 
and lower edges of fin pale 3 
3a. Median lateral black band which extends 
posteriorly from snout continuous with 
black posterior half of body; no dusky 
streak on cheek below eye; pale edges of 
caudal fin magenta in life; maximum 
standard length in excess of 80 mm. 
(Hawaiian Islands). 
Labroides phthirophagus, n. sp. 
3b. Median lateral black band which extends 
posteriorly from snout merges gradually 
to broad, pale-brown (dull-orange in life) 
area in center of body; a narrow dusky 
streak on cheek below eye running from 
chin to base of pectoral (may be faint in 
small adults); pale edges of caudal fin 
light lavender in life; maximum standard 
length about 60 mm. (Society Islands 
and Tuamotu Archipelago) 
Labroides rubrolabiatus, n. sp. 
Juvenile specimens for all species are un- 
available to me; however, all have been 
viewed underwater, frequently in the proxim- 
ity of adults. Juveniles of all four species ap- 
pear to have the same basic color pattern, 
namely black with a broad band of color 
along the back which extends and narrows on 
to snout. On L. dimidiatus and L. rubrolabiatus 
this band is brilliant deep blue (these species 
are readily separable by scale counts; see key 
above) ; on L. bicolor it is bright yellow; on L. 
phthirophagus it is bright purple. 
