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BULLETIN OF THE UNITED STATES FISH COMMISSION. 
C 3. In third and fourth foot the second joint of inner ramus has 2, the third joint 7 bristles; 
scapelliform terminal bristle of third joint of outer ramus in second to fourth foot much 
broader than in first pair C 4 
In third and fourth foot the second joint of inner ramus has 1, the third joint 5 bristles; 
scalpelliform terminal bristle of third joint of outer ramus in the first foot similar to that 
of second to fourth foot C 6 
C 4. Second joint of inner ramus of first foot without an inner marginal bristle; outer border of 
outer ramus not denticulate; terminal joint of inner ramus of first foot with 4 bristles; 
(female: abdomen with 2 or 3 segments; fifth foot 3 or 4-joiuted; terminal joint of anterior 
antennae at least twice as long as penultimate joint) * Calocalanus 
Second joint of inner ramus of first foot with an inner marginal bristle; outer border of outer 
ramus in more posterior feet denticulate; terminal joint of inner ramus of first foot with 5 
bristles; (female: abdomen with 4 segments; fifth foot 2-joiuted to lacking; terminal joint 
of anterior antennae, at most, 14 times as long as penultimate joint) C 5 
C 5. Third and fourth foot with denticulate outer border to the secoud joint of the outer ramus 
and to the proximal portion of the outer border in the third joint of the outer ramus; 
scalpelliform terminal bristle of the outer ramus of third foot little more than half as long 
as the third joint of the outer ramus; third joint of inner ramus of second foot with 6 
bristles (female : fifth pair absent or knob-shaped ; male : right fifth foot absent) Acrocalanus 
Third and fourth foot denticulate only on proximal portion of third joint of outer ramus; not 
on second joint; scalpelliform terminal bristle of outer ramus of third foot longer than 
third joint of the outer ramus; third joint of inner ramus of second foot with 7 bristles; 
(female: fifth foot 2-jointed; male: fifth foot 2-jointed) * Paracalanus 
C 6. Outer ramus of first foot 3-jointed; thorax without prickles (female: fifth foot wanting; male: 
neither foot of fifth pair biramous; right fifth foot sometimes wanting) * Eucalanus 
Outer ramus of first foot 2-jointed; middle thoracic segments with 1 or 2 pairs of prickles; 
(female: fifth foot 3-jointed; male: fifth foot 2-jointed) Rhincalanua 
C 7. Front with 2 large chitinous lenses * Mirada 
Front without chitinous lenses C 8 
C 8. Front conical, rounded anteriorly; cephalothorax very narrow; outer ramus of posterior 
antennae wanting Setella 
Front pointed; cephalothorax broader; outer ramus of posterior antennae 1-jointed C 9 
C 9. Furca with separate limbs (about twice as long as broad) and bristles much shorter than 
cephalothorax Euterpe 
Limbs of the very short furca as well as their two unusually long bristles fused in the middle 
line s. JEgisthus 
D. Head with dorsal eye-lenses; (posterior maxilliped 6-jointed, 6tli joint very minute). Labidocera 
Head without dorsal eye-lenses D 1 
D 1. Fifth pair of feet biramous with jointed inner ramus * Centropages 
Fifth pair of feet uniramous D2 
D 2. Posterior maxilliped 7-jointed D3 
Posterior maxilliped 3- to 4-jointed. D 5 
D 3. Furca long and slender, at least 6 times as long as broad; posterior maxilliped twice as long 
as anterior * Teniora 
Furca at most 4 times as long as broad; posterior maxilliped shorter than anterior D 4 
D4. Anterior maxilliped with short bristles on its proximal, and long, thick, sickle-shaped 
bristles on its distal portion, proximal basal joint of posterior maxilliped with a few short 
bristles * Candace 
Proximal and distal portions of anterior maxilliped and also proximal basal joint of the 
posterior maxilliped with long, prickly bristles Calanopia 
D 5. Outer ramus of posterior antenme shorter than distal joint of the inner ramus; anterior 
maxilliped provided on its proximal and distal portions with long, prickly bristles. Acartia 
Outer ramus of posterior antennae longer than distal joint of inner ramus ; anterior maxilliped with 
short bristles on proximal and powerful hooked bristles on distal part * Corynura 
E. Third joint of outer ramus of 2d to 4tli foot with 5 inner marginal bristles Spinocalanus $ 
Third joint of outer ramus of 2d to 4th foot with 4 inner marginal bristles El 
