11. ECOLOGY O F DISTRIBUTION
343
the subtropical convergence near 40'5, and the Antarctic Convergence
near 50"s.
Transition zone species
megalops.
Equatorial waters
Thysanopoda tricuspidata, T . orientalis, T . microphthalma;
Pseudeuphausia latifrons; Euphausia diomedeae, E . distinguenda,
E . pseudogibba, E. paragibba; Nematoscelis gracilis; Nematobrachion
Jlexipes.
Southern central or subtropical waters
Euphausia recurva, E . hemigibba.
Equatorial and central waters
Bentheuphausia amblyops; Thysanopoda monacantha, T . aequalisl
T . subaequalis (!), T . obtusifrons, T . pectinata; Euphausia wutica,
E . brevis, E . tenera; Nematoscelis tenella, N . micropslN. atlantica;
Nematobrachion boopis; Stylocheiron carinatum, S. afine, X. suhmii,
S . microphthalma, S. elongatum, S . longicorne, X. abbreviatum?,
S. maximum.
Localized distribution
Thysanopoda acutifrons; Thysanobsa gregaria; Nematoscelis
Euphausia gibboides, E . sanxoi.
Thysanopoda cornuta; Nematobrachion sexspinosum ('2 ); StyloRare species
cheiron indicum.
The amount of information on the distribution of euphausiids in the
Indian Ocean is increasing but is still not as great as our knowledge for
the Pacific and Atlantic Oceans. The distributional classification of
species given above is as yet only approximate and further information
may modify it considerably. Baker (1965) has studied the latitudinal
distribution of species of the genus Euphausia southwards through the
Indian Ocean to the Antarctic ; this and other information on latitudinal
distribution of the Indian Ocean species are summarized in Pig. 128.
Ponomareva (1964) examined the euphausiids of the Arabian Sea and
the Bay of Bengal. She finds one species, occasionally two species, to
be dominant in a haul unlike samples from the Indian Ocean and
regions of the Pacific where several species are present in fairly equal
numbers. The dominant species in the Arabian Sea are Euphausia
pseudogibba, E . diomedeae, and E . brevis. She points out that E . pseudoA.;M.l3-7
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