Munroe: Systematics of western Atlantic Symphurus 
107 
x=1.2). Lower head lobe width slightly less than 
postorbital length; considerably narrower than up- 
per head lobe. Snout long and somewhat rounded; 
covered with small ctenoid scales. Anterior nostril 
on ocular side short, when depressed posteriorly, 
usually falling just short of anterior margin of lower 
eye. Dermal papillae well developed on snout, chin, 
and dorsal portion of head at dorsal-fin base on blind 
side; larger specimens with dermal papillae extend- 
ing onto snout of ocular side of body. Jaws relatively 
short; maxilla extending posteriorly almost to verti- 
cal through middle of lower eye, occasionally only 
reaching vertical through anterior margin of pupil 
of lower eye. Ocular-side lower jaw with fleshy ridge 
near posterior margin. Teeth well developed on blind- 
side jaws. Ocular-side dentary usually with single, 
mostly incomplete, row of slender teeth along mar- 
gin; ocular-side premaxilla usually lacking teeth al- 
together, occasionally with small number of slender 
teeth on marginal portion of premaxilla anterior to 
vertical through base of anterior nostril. Chin depth 
usually slightly larger than snout length. Lower eye 
small; eyes usually equal in position, or occasionally 
upper slightly in advance of lower eye. Anterior and 
medial surfaces of eyes not covered with scales; usu- 
ally 1-3 small, ctenoid scales in narrow interorbital 
region. Pupillary operculum absent (occasional speci- 
mens with upper side of iris with irregular margin 
that may be remnant of small, poorly developed, 
pupillary operculum). Dorsal-fin origin usually equal 
to vertical through anterior margin of pupil of upper 
eye, occasionally with first dorsal-fin ray reaching 
vertical anterior to anterior margin of upper eye; 
predorsal length short. Blind sides of dorsal- and 
anal-fin rays (especially in posterior region of fins 
and in larger specimens) with single row of small, 
well-developed ctenoid scales extending from base 
to point about three-fourths length of fin ray. Larger 
specimens also with row of small, well-developed 
ctenoid scales extending from base to about three- 
fourths length of fin rays on ocular side of body. Pel- 
vic fin moderately long; longest pelvic-fin ray, when 
extended posteriorly, usually reaching base of first 
anal-fin ray. Posteriormost pelvic-fin ray connected 
to body by delicate membrane terminating immedi- 
ately anterior to anus, or occasionally extending pos- 
teriorly almost to base of anal-fin origin (membrane 
torn in most specimens). Caudal fin short. Scales 
large, strongly ctenoid on both sides of body. 
Pigmentation (Fig. 50J Body coloration similar for 
both sexes. Ocular surface uniformly dull tannish to 
dark brown with or without crossbands, or light to 
dark brown with sharply contrasting dark brown 
crossbands. Individuals from habitats with light-col- 
ored substrates generally with whitish ocular sur- 
face, with or without crossbands. Crossbands highly 
variable in number and degree of development but 
not continued onto dorsal and anal fins. Crossbands 
usually nearly completely continuous across body; 
those at midbody region often interrupted in mid- 
lateral region; crossbands relatively narrow cover- 
ing only 3-5 scale rows. Specimens lacking cross- 
bands with variable number of very dark, small 
specks scattered over ocular surface. Majority of 
larger specimens with large, conspicuous, black spot 
on upper lobe of ocular-side opercle ( usually faint or 
absent in smaller specimens; especially evident in 
recently preserved material). Inner linings of opercles 
and isthmus on both sides of body heavily pigmented. 
Gill filaments with conspicuous median line of dark 
pigment. Ocular-side upper lip with slight pigment 
band; ocular-side lower lip frequently spotted, but 
usually without definite pigment band. Blind side 
uniformly creamy white; occasional specimens with 
band of yellow pigment on blind side along body at bases 
of dorsal and anal fins. Peritoneum unpigmented. 
Dorsal and anal fins faintly or moderately dusky 
throughout their lengths, but without conspicuous 
spots or blotches. Dorsal- and anal-fin rays uniformly 
pigmented along their lengths. Membrane covering 
fin rays usually darker than membrane between fin 
rays and clearly outlining each fin ray. Caudal fin 
dusky throughout length, without spots or blotches. 
Size and sexual maturity (Fig. 9BJ Symphurus 
plagiusa attains a maximum standard length of ca. 
174 mm (Moe and Martin, 1965). The largest speci- 
men examined in the present study was 171 mm, 
but most were 120-150 mm. Of 568 fish examined, 
only about 4% exceeded 150 mm. Maximum total 
lengths of ca. 210 mm were reported for S. plagiusa 
collected on the continental shelf in the southern Gulf 
of Mexico and off South Carolina, respectively 
(Yanez-Arancibia and Sanchez-Gil, 1986; Wenner 
and Sedberry, 1989). Shealy et al. (1974) provided 
information on length-frequency relationships for 
this species; Jorgenson and Miller ( 1968) derived for- 
mulae for converting standard length and total length 
measurements; and Dawson (1965) calculated a 
length-weight formula for this species in the Gulf of 
Mexico. 
Among 191 specimens examined for life history 
information, were five fish (27.0-62.1 mm) for which 
sex was indeterminate, 64 were males (41.0-159 
mm), and 122 (34.0-157 mm) were females. No sig- 
nificant differences in sizes were observed between 
males and females. Based on reproductive stages of 
females, the estimated sizes at which S. plagiusa 
matures are between 85 and 95 mm. Of 85 mature 
