38
THE BIOLOGY OF EUPHAUSIIDS
3b. Upper eye with three crystalline cones in row
suhmii
3c. Upper eye with two crystalline cones in row
microphthalmu
3d. Lower eye more than three times as broad as upper eye at end.
Uropods do not reach tip of telson . . .. . . insulare
2b. Upper part of eye as broad or nearly as broad as lower part.
Numerous (more than 8) crystalline cones in transverse row.
4a. Sixth abdominal segment nearly three times as long as fifth
elongatum
4b. Sixth abdominal segment shorter than sum of lengths of fourth
and fifth ; eyes bilobate (see Silas and Mathew, 1967) indicuwz
4c. Sixth abdominal segment very little longer than fifth
longicorne
. .
lc. Penultimate segment of the elongated third pair of thoracic legs terminates in a true chela. Upper eye with or without slightly enlarged
crystalline cones.
5a. Fourth and fifth abdominal segments bear low, mid-dorsal keels.
Upper section of eye much smaller than lower, with numerous,
slightly enlarged, crystalline cones . . ..
abbreviatum
6a. Upper section of eye at most slightly smaller than lower,
with no enlarged crystalline cones
. . .. maximum
6b. Width of upper part of eye is approximately 0.7 that of
widest part of lower part of eye . . .. . . robustum
5b. Fourth and fifth abdominal segments without keels.
THE BIOLOGY OF EUPHAUSIIDS
3b. Upper eye with three crystalline cones in row
suhmii
3c. Upper eye with two crystalline cones in row
microphthalmu
3d. Lower eye more than three times as broad as upper eye at end.
Uropods do not reach tip of telson . . .. . . insulare
2b. Upper part of eye as broad or nearly as broad as lower part.
Numerous (more than 8) crystalline cones in transverse row.
4a. Sixth abdominal segment nearly three times as long as fifth
elongatum
4b. Sixth abdominal segment shorter than sum of lengths of fourth
and fifth ; eyes bilobate (see Silas and Mathew, 1967) indicuwz
4c. Sixth abdominal segment very little longer than fifth
longicorne
. .
lc. Penultimate segment of the elongated third pair of thoracic legs terminates in a true chela. Upper eye with or without slightly enlarged
crystalline cones.
5a. Fourth and fifth abdominal segments bear low, mid-dorsal keels.
Upper section of eye much smaller than lower, with numerous,
slightly enlarged, crystalline cones . . ..
abbreviatum
6a. Upper section of eye at most slightly smaller than lower,
with no enlarged crystalline cones
. . .. maximum
6b. Width of upper part of eye is approximately 0.7 that of
widest part of lower part of eye . . .. . . robustum
5b. Fourth and fifth abdominal segments without keels.