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Fishery Bulletin 96(1 ), 1998 
phurus plagusia is a medium-size tonguefish reach- 
ing a maximum known body size of about 130 mm 
and attaining sexual maturity as small as 80 mm. 
Symphurus tessellatus is a much larger species at- 
taining maximum known lengths of 220 mm and does 
not attain sexual maturity until reaching approxi- 
mately 120 mm. 
Some meristic values of S. plagusia overlap those 
of 11 other species of Atlantic tonguefishes. 
Symphurus plagusia occurs sympatrically, and oc- 
casionally syntopically, with S. diomedeanus but dif- 
fers from this species in having 12 caudal-fin rays 
(vs. 10 in S. diomedeanus) and in lacking the series 
of dark spots on posterior rays of the dorsal and anal 
fins and the pupillary operculum that are present in 
S. diomedeanus. Other differences between these 
species are discussed in the “Comparisons” section 
in the account of S. diomedeanus. 
Symphurus plagusia can be distinguished from S. 
plagiusa, which has an allopatric distribution in the 
western North Atlantic, in having 12 versus 10 cau- 
dal-fin rays. Symphurus plagusia also lacks the 
well-developed black pigment spot on the outer sur- 
face of the ocular-side opercle (present in S. plagiusa ), 
and in larger (>60 mm) S. plagiusa, there are 4-8 
ctenoid scales on blind-sides of the dorsal- and anal- 
fin rays (scales usually absent altogether, or occa- 
sionally 1-2 scales along bases of fin rays in S. 
plagusia). Other differences between these species 
are discussed in the “Comparisons” section in the 
account of S. plagiusa. 
Meristic values of S. plagusia overlap with those 
of six eastern Pacific species possessing either a 1-4-3 
or 1-5-3 ID pattern (Munroe, 1992). Of these, S. 
plagusia is most similar to S. melanurus in that both 
possess a fleshy ridge on the ocular-side lower jaw, 
and both have the first dorsal-fin ray reaching a ver- 
tical equal with, or anterior to, the anterior margin 
of the upper eye. The two species are distinguished 
in that S. plagusia lacks a pupillary operculum (vs. 
a weakly developed pupillary operculum usually 
present in S. melanurus), has fewer scales in longi- 
tudinal series (79-89 vs. 89-108 in S. melanurus), 
has a lightly pigmented inner lining on the blind- 
side opercle (vs. darkly pigmented inner lining on 
the blind-side opercle in S. melanurus), and in S. 
plagusia the posterior dorsal and anal fins and the cau- 
dal fin are not darker than the anterior regions (vs. 
progressive darkening in posterior dorsal and anal fins 
and darkly pigmented caudal fin in S. melanurus). 
