2. THE SPECIES OF KRILL
27
Order EUPHAUSIACEA
1. I n the male, the endopodites of the first and second pairs of
pleopods are not modified as copulatory organs and the basipodite of
the first pair of pleopods carries 1-6 spines. The endopodite of the
maxillule is two jointed. The endopodite of the maxilla is three jointed.
The outer plates of the uropods have a transverse suture. There are no
photophores. Eyes reduced in size. All eight thoracic legs well
developed.
Fam. BENTHEUPHAUSIIDAE Colosi, 1917
2 . In the male, the endopodites of the first and second pairs of
pleopods are modified as copulatory organs and the basipodite of the
first pair of pleopods has no spines. The endopodites of the maxillule
and maxilla are single jointed. The outer plates of the uropods have no
transverse suture. Photophores are present. Eyes well developed.
The last or the penultimate and last pair of thoracic legs are rudimentary.
Pam. EUPHAUSIIDAE Holt and Tattersall, 1905
Key t o genera of EUPHAUSIIDAE
la. Thoracic legs nearly uniform in structure.
2a. Eighth pair rudimentary.
3a. Seventh pair of same appearance as preceding.
Thysanopoda Milne-Edwards
3b. Seventh pair has endopodite of not more than two elongate
4a. Sixth and seventh pairs have exopodites in both sexes. Both
terminal and proximal processes of petasma are developed.
Meganyctiphanes Holt and Tattersall
4b. Sixth and seventh pairs have no exopodites in female. Both
terminal and proximal processes of petasma are lacking.
Nyctiphaizes G. 0. Sars
4c. Seventh pair has fully developed exopodites ; no endopodite
in males ; short, unjointed or two-jointed endopodite in
females.
ThysanoGsa Brandt (in part)
segments.
2b. Seventh and eighth pairs quite rudimentary.
5a. Distal three segments of sixth thoracic leg greatly reduced.
5b. Sixth thoracic leg similar in appearance to fifth.
Pseudeuphausia Hansen
Euphausia Dana
27
Order EUPHAUSIACEA
1. I n the male, the endopodites of the first and second pairs of
pleopods are not modified as copulatory organs and the basipodite of
the first pair of pleopods carries 1-6 spines. The endopodite of the
maxillule is two jointed. The endopodite of the maxilla is three jointed.
The outer plates of the uropods have a transverse suture. There are no
photophores. Eyes reduced in size. All eight thoracic legs well
developed.
Fam. BENTHEUPHAUSIIDAE Colosi, 1917
2 . In the male, the endopodites of the first and second pairs of
pleopods are modified as copulatory organs and the basipodite of the
first pair of pleopods has no spines. The endopodites of the maxillule
and maxilla are single jointed. The outer plates of the uropods have no
transverse suture. Photophores are present. Eyes well developed.
The last or the penultimate and last pair of thoracic legs are rudimentary.
Pam. EUPHAUSIIDAE Holt and Tattersall, 1905
Key t o genera of EUPHAUSIIDAE
la. Thoracic legs nearly uniform in structure.
2a. Eighth pair rudimentary.
3a. Seventh pair of same appearance as preceding.
Thysanopoda Milne-Edwards
3b. Seventh pair has endopodite of not more than two elongate
4a. Sixth and seventh pairs have exopodites in both sexes. Both
terminal and proximal processes of petasma are developed.
Meganyctiphanes Holt and Tattersall
4b. Sixth and seventh pairs have no exopodites in female. Both
terminal and proximal processes of petasma are lacking.
Nyctiphaizes G. 0. Sars
4c. Seventh pair has fully developed exopodites ; no endopodite
in males ; short, unjointed or two-jointed endopodite in
females.
ThysanoGsa Brandt (in part)
segments.
2b. Seventh and eighth pairs quite rudimentary.
5a. Distal three segments of sixth thoracic leg greatly reduced.
5b. Sixth thoracic leg similar in appearance to fifth.
Pseudeuphausia Hansen
Euphausia Dana