9. THE CLASS CRUSTACEA
299
bases of first antennae ; nauplius eye 0-2-0.27 mm from frontal margin ;
cephalothorax and free thoracic segments arched dorsally and turned
over ventrally, with latter segments projecting onward beyond former,
measuring 0.75 mm x 1.85 mm, 0.91 mm x 2.1 mm, and 0.9 mm x
1.9 mm respectively ; fifth segment markedly narrower, 0.33 mm long
x 0.7 mm wide, with a small rounded protuberance on each side in
young, with uneven but nearly parallel sides in adults ; genital segment
very short, 0-225 mm long x 0.6 mm broad, with somewhat convex
sides ; abdomen almost cylindrical, three- or four-segmented, 1-25 mm
x 0-5-0.6 m m ; caudal rami short, cigar-shaped, 0-66-0.66 mm x
0.21-0.23 mm, each with a fine seta on outer margin behind its middle
and five similar terminal setae, of which three are close together in the
middle ; eggs small, rounded, 0.060-0-080 mm in diameter, multiseriated ;
first antenna tapering gradually towards distal end, about 0.3 mm
long, of seven segments, armed with few setae, tipped with a medianlengthed and a few shorter setae; second antenna of five segments,
first segment enlarged, second the longest and with a spine on inner
margin, third short and with two setae a t distal end of inner margin,
terminal claw about 0.1 mm long ; first maxilla with two setae ; second
maxilla stout a t base, distal segment terminating in two setiform
pectinate rami, with a seta on inner margin ; maxilliped swollen, with
a digitiform process and two setae a t tip; first four legs biramous,
each basipodite comprised of two segments, with a seta on inner margin
of proximal segment, each ramus of three segments except endopodite
of fourth leg which consists of two ; fifth leg uniramous, plump, slightly
curved inward, tipped with a blunt spine-like inner process and a
simple outer seta.
Adult male (Fig. 197) with narrow body, 2.7-2.8 mm long, grayish
white, semi-transparent ; head subtriangular, with convex sides, 0.61mm
wide a t posterior end, wall fused with first thoracic segment, frontal
margin prominent, with rostrum projecting ventrad between bases of
first antennae; nauplius eye about 0.13 mm from frontal margin;
cephalothorax and free segments projecting ventrally on each side
but less conspicuously than in female ; first fused segment only slightly
narrower than head, wider than second ; second through fourth segments
diminishing in width posteriorly, measuring 0.20-0.21 mm x 0.51 mm,
0.18-0.19 mm x 0.41-0-42 mm, and 0.225 mm x 0.338 mm respectively ; fifth segment strongly constricted off from fourth, fused with
genital segment; genital segment 0.34-0-4 mm x 0-4-0-21 mm, with
convex sides ; abdomen nearly cylindrical, of three segments, 0.65 mm
long; first segment rounded, 0.2 mm long x 0.3 mm wide, second
segment rounded but shorter, third segment 0.3-0.31 mm x 0.24-
299
bases of first antennae ; nauplius eye 0-2-0.27 mm from frontal margin ;
cephalothorax and free thoracic segments arched dorsally and turned
over ventrally, with latter segments projecting onward beyond former,
measuring 0.75 mm x 1.85 mm, 0.91 mm x 2.1 mm, and 0.9 mm x
1.9 mm respectively ; fifth segment markedly narrower, 0.33 mm long
x 0.7 mm wide, with a small rounded protuberance on each side in
young, with uneven but nearly parallel sides in adults ; genital segment
very short, 0-225 mm long x 0.6 mm broad, with somewhat convex
sides ; abdomen almost cylindrical, three- or four-segmented, 1-25 mm
x 0-5-0.6 m m ; caudal rami short, cigar-shaped, 0-66-0.66 mm x
0.21-0.23 mm, each with a fine seta on outer margin behind its middle
and five similar terminal setae, of which three are close together in the
middle ; eggs small, rounded, 0.060-0-080 mm in diameter, multiseriated ;
first antenna tapering gradually towards distal end, about 0.3 mm
long, of seven segments, armed with few setae, tipped with a medianlengthed and a few shorter setae; second antenna of five segments,
first segment enlarged, second the longest and with a spine on inner
margin, third short and with two setae a t distal end of inner margin,
terminal claw about 0.1 mm long ; first maxilla with two setae ; second
maxilla stout a t base, distal segment terminating in two setiform
pectinate rami, with a seta on inner margin ; maxilliped swollen, with
a digitiform process and two setae a t tip; first four legs biramous,
each basipodite comprised of two segments, with a seta on inner margin
of proximal segment, each ramus of three segments except endopodite
of fourth leg which consists of two ; fifth leg uniramous, plump, slightly
curved inward, tipped with a blunt spine-like inner process and a
simple outer seta.
Adult male (Fig. 197) with narrow body, 2.7-2.8 mm long, grayish
white, semi-transparent ; head subtriangular, with convex sides, 0.61mm
wide a t posterior end, wall fused with first thoracic segment, frontal
margin prominent, with rostrum projecting ventrad between bases of
first antennae; nauplius eye about 0.13 mm from frontal margin;
cephalothorax and free segments projecting ventrally on each side
but less conspicuously than in female ; first fused segment only slightly
narrower than head, wider than second ; second through fourth segments
diminishing in width posteriorly, measuring 0.20-0.21 mm x 0.51 mm,
0.18-0.19 mm x 0.41-0-42 mm, and 0.225 mm x 0.338 mm respectively ; fifth segment strongly constricted off from fourth, fused with
genital segment; genital segment 0.34-0-4 mm x 0-4-0-21 mm, with
convex sides ; abdomen nearly cylindrical, of three segments, 0.65 mm
long; first segment rounded, 0.2 mm long x 0.3 mm wide, second
segment rounded but shorter, third segment 0.3-0.31 mm x 0.24-