Anthessius - — Illg 
355 
esses, these less well developed than those of 
basal segments. Each segment with dense row 
of cilia on lateral margin, distal 2 segments with 
medial cilia. Spines of terminal segment with 
hyaline flanges. All setae of leg with plumose 
ciliation. 
Fifth legs (Fig. 38) with probably 2 seg- 
ments represented, basal consisting only of ex- 
pansion on body segment posteriorly and lat- 
erally to furnish articulation of distal segment, 
but with 1 small seta representing armature. 
Second segment elongate, flat, with cuticularized 
medial and lateral margins. Length about 4 times 
greatest width. Armature 3 spines and 1 seta, 
spines about equally spaced on lateral and ter- 
minal margins: 1 lateral spine at about distal 
three-fourths of lateral margin, 1 lateral spine 
at about distal .9 of margin; 1 seta inserted close 
to lateral distal spine; 1 apical spine at medial 
distal corner. Spines subtended by small groups 
of spinules and cuticular spinous processes. 
Spinules of apical spine extending briefly on 
medial margin to form short row. 
Sixth legs probably represented by small 
setiferous knob (Fig. 38) in depression at 
aperture of oviduct, located dorsally on lateral 
expansion of genital segment. Two subequal 
setules forming armature. 
Caudal ramus (Fig. 39) about 2.6 times as 
long as greatest width and nearly as long as 
anal segment. Margins with conspicuous artic- 
ular development and some surface ornamenta- 
tion. Armature consisting of 6 setae. Of apical 
quartet of setae, medial of central 2 longest, 
about 3.5 times as long as ramus, adjacent seta 
2.2 times length of ramus. Medial apical seta 
about .73 times as long as ramus; lateral apical 
seta about .55 times as long as ramus. Lateral 
marginal seta about .5 as long as ramus, inserted 
on lateral margin at about distal .6. Dorsal seta 
short, not quite as long as width of ramus, in- 
serted medially just subapically. 
male (Figs. 44-58) : Body length 2.53 mm., 
greatest width 0.94 mm., based on 6 specimens. 
Body (Figs. 48, 49) very generalized cyclopoid 
in type. Cephalosome bearing first legs, segment 
of these appendages strongly indicated by in- 
dentations. Metasome of free segments of legs 
2 to 4. Segment of leg 4 lacking auxiliary lobe- 
like elements seen in female. Urosome of seg- 
ments of legs 5, 6, and 4 abdominal segments. 
Segments of legs 5 and 6 much coalesced in a 
genital complex containing elongate sperma- 
tophores. Segment of leg 5 without epimera. 
Antennule (Fig. 50) similar in proportions, 
segmentation and armature to that of female, 
but with dimorphism expressed in more highly 
developed aesthetes and greater number of 
aesthetes. Segment 2 has 2 conspicuous aesthetes 
accompanying basal group of 7 setae and 1 
aesthete accompanying terminal group of 8 
setae. Segment 4 has conspicuous aesthete ac- 
companying 3 setae. In segments 5, 6, 7, aes- 
thetes, corresponding to those of the female 
are present, but tending to be longer. 
Antennae and mouthparts, except maxilliped, 
much as in female. Antenna ( Fig. 51); man- 
dible (Fig. 52); maxillule (Fig. 53); maxilla 
(Fig. 54). 
Maxilliped (Fig. 55) highly dimorphic, de- 
veloped as massive, complicated appendage, 
possibly trimerous. In mouth area, maxilliped 
held in characteristic posture. First segment not 
as long as second, unornamented. Second seg- 
ment somewhat tapered apically, margin medial 
in position in normal posture bearing ornamen- 
tation serving to act in conjunction with claw- 
like terminal segment in prehensile function. 
Medial ornamentation consisting of patches of 
denticles. In addition, near midpoint of medial 
margin a short, stout spine. Terminal segment 
forming very complicated region of articula- 
tion on apex of second segment, prolonged as 
curving claw, longer than second segment. One 
seta, accompanied by 1 setule, inserted on ex- 
panded region of articulation. 
Dimorphism also expressed particularly in 
first legs, remaining swimming legs very sim- 
ilar to those of female. Protopodites and exop- 
odites of first legs (Fig. 44) essentially as in 
female. Basal segments of endopodites as in 
female, terminal segment of each with 1 lateral 
Figs. 40-47: Anthessius lighti, new species. The scales accompanying certain figures represent 0.1 mm. 
Female: 40, first leg; 41, second leg; 42, third leg; 43, fourth leg. Male: 44, first leg; 45, second leg; 46, 
third leg; 47, fourth leg. 
