CLASS ACANTHARIA

Usually with 10, 16, 20 or 32 strontium sulfate spicules radiating from the center of the cell; all marine; outer vacuolated layer enclosed by a sheath or envelope; an inner mass sometimes enclosed within a fibrous capsule; often with large numbers of endosymbionts; flagellated stages produced by some (these have laterally inserted flagella, one directed anteriorly and the other directed posteriorly). This class has 4 orders.

• ORDER HOLACANTHIDA
  • Simple acantharians in which the spines simply cross; no capsular membrane.
  • Acanthochiasma, Acanthoplegma, Acanthocolla, Acanthospira, Acanthocyrtha.

• ORDER SYMPHYACANTHIDA
  • Bases of the 20 radial spines fused into a star-like structure called a central body; no capsular membrane.
  • Acantholithium, Astrolithium, Astrolonche, Heliolithium, Amphilithium, Pseudolithium, Dicranophora, Haliommatidium.

• ORDER CHAUNACANTHIDA
  • Spines 20; 4-sided; bases loosely articulated; no capsular membrane.
  • Gigarticon, Heteracon, Amphiacon, Stauracon, Conicon.

• ORDER ARTHRACANTHIDA
  • Have a capsular membrane; bases of the 20 radial spines are pyramidal with 5-6 faces; spines joined at the base to make a star-like body or a leaf-like body.
  • Acanthometra, Amphilonche, Tetralonche, Pleuraspis, Lynchaspis, Icoaspis, Dorataspis, Coscinaspis, Craniaspis, Siphonaspis, Aconthaspis, Hystrichaspis, Dictyaspis, Phractopelta, Lithoptera, Coelaspis, Hexalaspis, Hexaconus, Phyllostaurus, Amphistaurus, Acanthostaurus, Lonchostaurus, Zygostaurus, Phatnacantha, Stauracantha, Xiphacantha, Pristacantha, Dictyacantha, Stauraspis, Diploconus.

CLASS POLYCYSTINEA

Silicaceous skeleton of solid elements in a latticed shell with or without radial spicules; some make biflagellate swarmer cells (crystal swarmers); cytoplasm divided into inner and outer regions by a central capsule which is perforated by many pores; microtubular supports for the axopods arise in the cytoplasm; often with symbiotic algae. This class has 3 orders.

• ORDER THALLASIOCOLIDA (SPUMELLARIA OR PERIPYLEA)
  • Pores uniformly distributed in capsular membrane; skeleton absent or of spicules or of 1 or more concentric latticed shells.
  • Thallasiocola, Thalassiolampe, Sphaerozoum, Raphidozoum, Thalassosphaera, Thalassoxanthum, Physematium, Thalassoplancta, Lampoxanthium, Tholostaurus, Styptosphaera, Plegmosphaera, Collosphaera, Arcosphaera, Buccinosphaera, Siphonosphaera, Disolenia, Otosphaera, Cenosphaera, Cladococcus, Acanthosphaera, Centrocubus, Octodendron, Spongoliva, Spongosphaera, Spongoplegma, Didymocyrtis, Carposphaera, Thecosphaera, Saturnalis, Stylacontarium, Stylatractus, Staurolonche, Hexalonche, Hexacontium, Cromyechinus, Astrosphaera, Actinomma, Larcopyle, Larcospira, Octopyle, Tetrapyle, Hexapyle, Pylolena, Spongocore, Spongurus, Heliodiscus, Amphirhopalum, Ommatodiscus, Stylochlamydium, Stylodictya, Spongopyle, Spongotrochus, Spongaster, Euchitonia, Hymeniastrum, Orosphaera, Thalassiothamnus, Bathysphaera, Thalassophysa, Collozoum, Actissa, Centrocolla.

• ORDER HOLLANDOSPHAERIDA (PERIAXOPLASTIDA) TENTATIVE GROUP
  • Axoplast near to the nucleus; microsphere near axoplast and is intracapsular.
  • Hollandosphaera, Stigmosphaera, Heliosoma, Cyrtidosphaera, Cenellispis, Spongoliva, Panartus, Astrophacus, Euchitonia, Triolena, Monozonium, Tetrapyle.

• ORDER NASSELLARIDA (NASSELLARIA, MONOPYLEA)
  • Capsular membrane with pores at one pole; skeleton formed of spines and connecting bars from a single element; often conical.
  • Triplagia, Triplecta, Phormacantha, Zygocircus, Acanthodesmia, Lophospyris, Nephrospyris, Lithocircus, Neosemantis, Pseudocubus, Lithopera, Lophophaen Peromelissa, Arachnocorys, Cycladophora, Clathrocanium, Callimitra, Clathrocorys, Sethophormis, Lampromitra, Euecryphalus, Theopilium, Litharachnium, Cornutella, Peripyramis,Carpocanistrum, Antarctissa, Acanthocorys, Pterocanium, Dictyophimus, Lipmanella, Clathrocyclas, Cyrtopera, Stichopilium, Lithostrobus, Eucyrtidium, Spirocyrtis, Phormostichoartus, Siphocampe, Botryostrobus, Lyriospyris, Dendrospyris, Triceraspyris, Tholospyris, Phormospyris, Anthocyrtidium, Lamprocyrtis, Thecocorythium, Lamprocyclas, Pterocorys, Centrobotrys, Saccospyris, Acrobotrys, Botryopyle, Plagonidium, Cortina, Semantis, Zygostephanus, Prismatium, Anthospyris, Lophospyris, Rhodospyris, Amphispyris, Cyrtocalpis, Eucecryphalus, Pterocorys, Botryopera.

CLASS TAXOPODEA

Four rows of flattened mobile axopodia (they can row themselves through the water) with ball and socket joints associated with the nucleus.

• ORDER STICHOLONCHIDA (TAXOPODIA)
  • Cell bilaterally symmetrical; rowing axopods which arise from microtubular organizing centers on the nuclear membrane; silicaceous spicules.
  • Sticholonche.