Revision of Plesiops — INGER 
261 
this sculpturing are present in the entire upper 
half of the body; in an adult (48.5 mm.) all 
of the body scales have a delineated central 
area. The larger species corallicola (Fig. Id) 
shows the same phenomenon, but with cor- 
responding stages at greater lengths. For 
example, a 29.0 mm. fish has no scales with 
an outlined center; but such marked scales 
occur on the body between the axilla and the 
level of the soft dorsal in one 40.5 mm. long 
and over the entire body in one 58.0 mm. 
long. A young nigricans (34.0 mm.) has the 
characteristic plesiopine scales in the center 
of the body from the axilla to the end of the 
pectoral. 
The division of the lower pectoral rays (Fig. 
2) increases with size in two of the larger 
species. The type of nigricans (132 mm. total 
length) has four branches in each of the two 
lowest rays, five in the next ray, six in the 
next, and eight in each of the two next above. 
In Ruppell’s second sepcimen (117 mm. total 
length, approx. 90 mm. standard length) the 
numbers of branches on the six lowest rays 
are 4, 6, 6, 8, 6, and 9 respectively, counting 
up from the ventral margin of the fin. (Data 
on both of these specimens are from Dr. 
Zilch.) The numbers of branches in a smaller 
individual (USNM 147530; 34.0 mm.) are 2, 
4, 4, 4, 4, and 4. The same kind of variation, 
illustrated in Table 1, occurs in corallicola 
(Fig. 2b, c). 
Plesiops multisquamata , the third large spe- 
cies, also has multibranched lower pectoral 
rays; but no information on ontogenetic 
changes is available. 
The remaining species, which are smaller 
(maximum observed standard lengths in oxy- 
cephalus 65.5 mm.; gravid female of cephalo- 
taenia 35.0 mm.; gravid female of coeruleolin- 
eatus 38.0 mm.), have only one or two branches 
in the lowest three pectoral rays and an ob- 
served maximum of four branches in the 
sixth ray, counting from the ventral edge 
(Fig. 2a). The frequency of individuals hav- 
ing two, three, or four branches in the sixth 
ray is shown in (Table 2). 
Fig. 2. Branching of rays in pectoral fins of: a, P. 
. coeruleolineatus (X 5.3); b, P. corallicola (X 2.6); c, 
detail of lowest pectoral rays of corallicola (greatly 
enlarged). 
