260 
PACIFIC SCIENCE, Vol. IX, July, 1955 
Plesiops Cuvier 
Dorsal X-XIII, 6-8, usually XI, 7 or XII, 
7; anal III, 8; dorsal and anal spines pungent; 
dorsal membrane extending beyond tips of 
spines, incised at least before anterior spines; 
anal membrane usually incised before last two 
spines; pelvic I, 4; the first soft ray thickened 
and elongated, reaching at least to anal origin; 
all soft pelvic rays branched. 
Vomerine and palatal teeth present, in 
bands; no lingual teeth; lower pharyngeal 
teeth acute; opercle without spines; pseudo- 
branchiae present. 
Head naked before orbit; post-orbital part 
of head with cycloid scales; body scales 
mostly ctenoid, with a sharply outlined center 
(Fig. 1) in adults; two lateral lines, the upper 
curving with the body profile and ending 
opposite or just behind last dorsal ray. 
The peculiar scales with their distinctly out- 
lined center, first noted by Riippell (1828), 
distinguish Plesiops from the related genera 
Paraplesiops Bleeker and Barrosia Smith. Para- 
plesiops also differs from Plesiops in its posses- 
sion of lingual teeth and obtuse lower pharyn- 
geal teeth. The first soft pelvic ray in Barrosia 
is only feebly thickened. The dorsal mem- 
brane, scarcely notched, also distinguishes 
Barrosia from Plesiops . 
Smith (1952) places Plesiops altivelis Stein- 
dachner, known only from the type specimen, 
in his newly defined genus Barrosia. Notes 
on the type of altivelis made by Dr. Kahsbauer 
confirm Smith’s conclusion. The first pelvic 
ray of altivelis is not thickened and the lower 
pectoral rays have only one branch each. The 
former character separates altivelis from all 
species of Plesiops and the latter from the 
larger species, with which altivelis corresponds 
in size (standard length 100 mm.). 
Plesiops gigas Steindachner (type locality 
Australia) belongs in the genus Paraplesiops 
as is indicated by its high soft anal and dorsal 
counts (11-12), the large number of scales 
(mid-lateral series 43), and the presence of 
lingual teeth. 
Fig. 1. Body scales of three species of Plesiops. a, P. 
corallicola; b, P. cephalotaenia; c, P. oxycephalus. 
Assessor macneilli Whitley (type locality 
Queensland), described as being * 'superfi- 
cially like a Plesiops is of uncertain position 
because of the inadequate description given 
by Whitley (1935). The figure published sub- 
sequently by Whitley (1940) does indeed 
resemble Plesiops in habitus. The shape of the 
pelvics, the number of soft pelvic rays, the 
interruption of the lateral line, and the absence 
of lingual teeth also suggest relationship to 
Plesiops. However, the original description 
notes the presence of scales on the maxillary, 
the absence of palatal teeth, and the scarcely 
notched dorsal membrane, all of which char- 
acters would separate Whitley’s species from 
Plesiops. Thickening of the first soft pelvic ray, 
diagnostic of Plesiops , is not mentioned by 
Whitley. 
Notes on Ontogenetic Variation 
Certain characters, such as the degree of 
branching in the lower pectoral rays and the 
development of an outlined circular or oval 
center on the scales, apparently change with 
age. Considering the latter character first, in 
cephalotaenia (Fig. lb) an outlined center oc- 
curs only on the scales in the upper half of 
the middle third of the body in a fish 27.0 
mm. long; in one 28.5 mm. long, scales with 
