A Revision of the Fishes of the Genus Plesiops Cuvier 
Robert F. Inger 1 
In the course of a routine examination of 
the plesiopids in the collections of the Chi- 
cago Natural History Museum, a specimen 
of Plesiops oxycephalus Bleeker, previously re- 
corded only by Bleeker, and four specimens 
of an undescribed species mislabeled P. nigri- 
cans and P. melasvsesQ found. These discoveries 
and the observation made by Smith (1952) 
that Indo-Pacific references to nigricans were 
incorrect prompted a study of the entire genus. 
Throughout this study Mr. L. P. Woods, 
Chicago Natural History Museum, was con- 
sulted on many points; his helpful advice and 
reading of the manuscript are greatly appre- 
ciated. I am grateful to Dr. L. P. Schultz, 
United States National Museum, for his 
critical reading of the manuscript and for the 
loan of an extensive collection of Plesiops. 
Thanks are also due to Mr. N. B. Marshall, 
British Museum (Natural History), for the 
loan of Red Sea material; to Dr. P. Kahs- 
bauer, Naturhistorisches Museum, Vienna, 
for notes on the type of Plesiops altivelis 
Steindachner; to Dr. A. Zilch, Senckenberg- 
ische Naturforschende Gesellschaft, for data 
and photographs of Ruppell’s specimens of 
nigricans and coeruleolineatus\ and to Dr. K. 
H. Barnard, South African Museum, for data 
on Natal specimens at his disposal. The fig- 
ures are the work of Miss Margaret Bradbury, 
Chicago Natural History Museum. 
Methods of Counting and Measuring 
All fin rays with separate bases were 
counted. Lateral line scale counts include only 
1 Chicago Natural History Museum. Manuscript 
received December 1, 1954. 
tubulated scales. In the upper lateral line the 
count begins at the upper corner of the gill 
opening. The lower lateral line ends at the 
caudal flexure. The mid-lateral scale count 
starts at the gill opening just above the pec- 
toral base and ends at the caudal flexure. A 
transverse series of scales was counted from 
the origin of the dorsal fin caudad and ven- 
trad to the lateral line. A second transverse 
series was counted from the origin of the anal 
fin forwards and upwards to the lateral line. 
Neither transverse series includes the lateral 
line scale or fin sheath scales. Gill raker counts 
include all rudiments and developed rakers 
on the first arch. The raker at the angle is 
considered as part of the upper limb. 
Measurements up to 120 mm. were made 
with vernier calipers graduated to 0.1 mm. 
In the few instances of larger fishes, a steel 
rule calibrated in half millimeters was used. 
All measurements are given to the nearest 
half millimeter. Standard length is taken as the 
distance from the tip of the head to the caudal 
flexure, head length as the distance between 
the forward tip and the end of the gill mem- 
brane, and body depth as the maximum 
depth. Head length and body depth are pre- 
sented as the ratio of standard length to these 
dimensions and are cited as "head” and 
"depth.” Unless specifically stated otherwise, 
"length” signifies standard length. 
Counts of all species are summarized in 
Table 3. 
Except where noted the descriptions are 
based upon many individuals. 
The abbreviations CNHM and USNM refer 
to the Chicago Natural History Museum and 
the United States National Museum. 
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