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| | Crustacea |
 | | Notostraca- tadpole shrimps, sessile eyes, antennae reduced, depressed body, large shield-like univalved carapace, many pairs of thoracic appendages, about 11 widely distributed species, all freshwater. |
 | | Conchostraca- clam shrimps, completely enclosed within a bivalved carapace, sessile eyes, second antennae used for swimming, many trunk appendages, 180 species, all freshwater. |
 | | Cladocera- water fleas, bivalved carapace covers only the trunk, large and sessile eyes, large second antennae used for swimming, only 4-6 trunk appendages, body segments fused, egg brooders, 450 species, mostly freshwater, planktonic and littoral. |
| www.esg.montana.edu /dlg/aim/crustac/crustac.html (1487 words) |
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