Order Spumellaria

Family Actinommidae

	Acanthosphaera actinota (Haeckel) (Figure 15.25) [=Acanthosphaera tenuissima]. Single shell with large, regular polygonal meshes separated by very thin bars. Nodal points bear short, bristle-shaped spines; no primary (conspicuously larger) radial spines (broken-off on specimen photographed). Shell diameter: 60-90 µm. Ref: Boltovskoy and Riedel (1980).
	Acanthosphaera dodecastyla Mast (Figure 15.26). Single shell with large circular pores with very conspicuous polygonal frames, many (10-20) robust, three-bladed spines. Shell diameter without spines: 50-80 µm. Ref: Popofsky (1913), Boltovskoy and Riedel (1980).
	Acanthosphaera pinchuda Boltovskoy and Riedel (Figure 15.28). Single shell with regular, subcircular pores surrounded by conspicuous protruding frames which extend into thin, thread-like spines at the nodal points. No primary (conspicuously larger) radial spines. Shell diameter without spines: 90-120 µm. Ref: Boltovskoy and Riedel (1980).
	Actinomma antarcticum (Haeckel) group? (Figure 15.48) [=Diploplegma banzare, Diploplegma aquatica]. Three concentric shells. Cortical shell composed of a very irregular, sometimes sponge-like network of thick anastomosing bars. Second shell large, irregularly shaped, spongy. First shell small, circular, rarely visible. Nigrini (1967) described Actinomma medianum, which difffers from A. antarcticum in that it has a simply latticed cortical shell and a more delicate medullary meshwork. Cortical shell diameter: 200-400 µm. Ref: Riedel (1958), Nigrini (1967).
	Actinomma arcadophorum Haeckel (Figure 15.49). Medullary shells similar to Actinomma antarcticum; cortical shell is composed of an irregular, sponge-like or lace-like network of very thin, delicate anastomosing bars. Cortical shell diameter: 200-250 µm. Ref: Haeckel (1887), Nigrini and Moore (1979).
	Actinomma leptodermum (Jorgensen) (Figure 15.37) [=Echinomma leptodermum]. Three concentric shells, pores on outermost shell relatively large, subcircular, irregularly arranged; surface covered by numerous short three-bladed spines; no primary (conspicuously larger) radial spines. Outermost shell diameter without spines: 60-120 µm. Ref: Nigrini and Moore (1979).
	Actinomma sol Cleve (Figure 15.44) [=Thecosphaera radians]. Three concentric shells. Outermost with regular, circular pores with well developed polygonal frames, usually bearing short bristle-shaped spines on the nodes (broken off in the specimen photographed); no primary (conspicuously larger) radial spines (see remark for Thecosphaera inermis). Outermost shell diameter: 70-100 µm. Ref: Hollande and Enjumet (1960), Boltovskoy and Riedel (1980).
	Arachnosphaera myriacantha Haeckel (Figure 15.45). Fully grown specimens with many (up to over seven; four in the specimen illustrated) concentric spheres, the innermost with regular hexagonal meshes and cylindrical spines arising from the nodes. At regular distances these spines produce branches which anastomose laterally forming subsequent spheres with a delicate, irregular, cobweb-like network. Branching spines protrude from the surface of the last shell. Diameter of innermost shell: ca. 100 µm. Ref: Haeckel (1862).
	Astrosphaera hexagonalis Haeckel (Figure 15.40). Two shells and many (>6) primary radial spines. Inner shell with regular polygonal meshes and thin bars. Outer shell with very large, triangular meshes formed by anastomosing of lateral branches produced by the long, three-bladed primary spines arising from the first shell. Spines extend beyond the very open outer shell. Diameter of inner shell: 150 µm. Ref: Haeckel (1887).
	Carposphaera acanthophora (Popofsky) (Figure 15.39). One latticed cortical shell and one medullary shell represented by an irregular formation of anastomosing centripetal bars arising from the cortical shell (may be missing in poorly preserved materials; not focused in specimen illustrated). Pores on outer shell irregular in shape and size, generally subcircular. Surface rough or thorny. Diameter of cortical shell: 150-270 µm. Ref: Benson (1966).
	Cenosphaera spp. group (Figure 15.29) [=Cenosphaera elysia, C. compacta, C. hirsuta]. Single sphere, often thick-walled. Pores more or less regular, circular, or irregular, of variable shape and size, with or without polygonal frames, with or without thin, bristle-shaped by-spines or thorns. No primary (conspicuously larger) radial spines. Highly variable group with many different morphotypes present chiefly in middle and high latitudes (e.g., C. cristata Haeckel in Antarctic waters, cf. Petrushevskaya 1967; C. compacta Haeckel and C. elysia Haeckel in subantarctic-transitional areas, cf. Boltovskoy and Riedel 1980). Shell diameter: 50-320 µm. Ref: Petrushevskaya (1967), Boltovskoy and Riedel (1980).
	Centrocubus cladostylus Haeckel (Figure 15.58). Medullary shell single, composed of bars that define a small cube (Figure 2C); cortical shell a spongy meshwork arising immediately from the medullary shell, supported by many large, three-bladed spines that protrude outside of the spongy mass. Cortical shell diameter without spines: 150-200 µm. Ref: Haeckel (1887).
	Cladococcus cervicornis Haeckel (Figure 15.41). Single shell with very irregular sub-polygonal pores; at many nodal points slightly curved, cylindrical spines project radially dichotomizing repeatedly starting about 2/3 of the way from the cortical shell. Shell diameter without spines: ca. 70 µm. Ref: Boltovskoy and Riedel (1980).
	Cladococcus megaceros Hollande and Enjumet (Figure 15.42). Similar to Cladococcus cervicornis, differs in that spines can be three-bladed, thickening toward their distal end; branches are short and dull, resembling the horns or a reindeer. Pores are more irregular in size and shape. Shell diameter without spines: ca. 60 µm. Ref: Hollande and Enjumet (1960), Boltovskoy and Riedel (1980).
	Cromyechinus antarctica (Dreyer) (Figure 5A, 5A', 14, 15.30). Fully grown specimens with four concentric, latticed shells. Outermost thin-walled, with very small pores. Third shell thicker, with large, irregularly shaped pores. Surface covered with many short, stout, three-bladed spines, at one of the poles spines may be denser and larger, forming a pylome. Major diameter of outermost shell: 100-160 µm. Ref: Petrushevskaya (1967).
	Cromyechinus icosacanthus Haeckel (Figure 2B). Fully grown specimens with four latticed concentric shells and many (>6) stout, three-bladed spines. Outermost shell thin-walled, delicate, with very small, regular, circular pores. Third shell with large, irregular, polygonal pores. Outermost shell diameter without spines: ca. 160 µm. Ref: Haeckel (1887).
	Cromyomma circumtextum Haeckel (Figure 15.47). Fully grown specimens with four latticed concentric shells and many three-bladed spines of irregular size and distribution. Outermost shell very delicate, thin-walled, with thread-like bars and large, irregular, polygonal meshes; third shell with large, irregular pores and thick bars. Due to its delicacy, the fourth shell is very likely to be absent in sedimentary materials, in which case this species may be identified as Hexalonche aristarchi (see below). Outermost shell diameter without spines: ca. 220 µm. Ref: Haeckel (1887).
	Druppatractus irregularis Popofsky (Figure 15.27). Two latticed shells, outermost thin-walled, smooth, with small regular, circular pores; medullary shell pear-shaped. Two main polar spines of equal or different size (additional, usually smaller spines may be present as well). Cortical shell diameter without spines: ca. 80 µm. Ref: Benson (1966).
	Heliaster hexagonium Hollande and Enjumet (Figure 15.46). Two latticed shells, medullary as in Carposphaera acanthophora (may be missing in poorly preserved materials). Pores on cortical shell very regular, polygonal, with thin bars; bristle-shaped spines on nodes. Outer shell diameter without spines: ca. 230 µm. Ref: Hollande and Enjumet (1960).
	Heliosoma echinaster Haeckel (Figure 15.43) [=Tetrapetalon elegans]. Two concentric shells. Medullary shell composed of a loose network of thin anastomosing bars. Outer shell similar to that of Heliaster hexagonium, except for the presence of many (>6) long, three-bladed primary spines. Outer shell diameter without spines: ca. 160 µm. Ref: Hollande and Enjumet (1960).
	Hexacontium aristarchi (Haeckel) (Figure 15.33) [=Hexalonche aristarchi]. Similar to Hexacontium armatum/hostile, except that pores on outermost shell are larger and more irregular in size and distribution. May have one medullary shell (?). It is probable that H. aristarchi is a developmental form of Cromyomma circumtextum, from which it differs by lacking the outermost, very slender and delicate fourth shell. Outermost shell diameter without spines: ca. 130 µm. Ref: Boltovskoy and Riedel (1980).
	Hexacontium armatum/hostile Cleve group (Figure 15.32). [=Hexacontium armatum, Hexacontium hostile, ?Hexacontium entacanthum]. Three concentric latticed shells; surface of outermost usually thorny or spiny, pores medium-sized, regular or irregular in size and distribution, with or without polygonal frames. Usually 6 main spines opposite in pairs in three dimensive axes perpendicular to one another. Outermost shell diameter without spines: 70-100 µm. Poorly defined morphotype, probably includes several related species. Ref: Boltovskoy and Riedel (1980).
	Hexacontium laevigatum Haeckel (Figure 15.31). Similar to Hexacontium armatum/hostile, except that the surface of the outermost shell is smooth, and pores are smaller, circular, unframed of regular size and distribution. Outermost shell diameter without spines: 70-120 µm. Ref: Benson (1966), Nigrini and Moore (1979).
	Octodendron cubocentron Haeckel (Figure 15.56). Similar to Centrocubus cladostylus, except that spongy meshwork starts at some distance from the cubical medullary shell. Outer shell diameter without spines: ca. 200 µm. Ref: Haeckel (1887).
	Plegmosphaera entodictyon Haeckel (Figure 15.54). Shell is a spongy mass with a central cavity; the spongy meshwork is denser in the vicinity of the central cavity than at the periphery of the shell. Shell diameter: ca. 200 µm. Ref: Hollande and Enjumet (1960).
	Plegmosphaera exodictyon Haeckel (Figure 15.55). Similar to Plegmosphaera entodictyon, except that the spongy meshwork is denser both in the vicinity of the central cavity and at the periphery of the shell, and looser midway. Shell diameter: ca. 400 µm. Ref: Haeckel (1887).
	Plegmosphaera pachyplegma Haeckel (Figure 15.53). Similar to Plegmosphaera entodictyon, except that the spongy meshwork is denser at the periphery of the shell than in the vicinity of the central cavity. Shell diameter: ca. 200 µm. Ref: Hollande and Enjumet (1960).
	Saturnalis circularis Haeckel (Figure 15.36). Two concentric latticed shells, the cortical with circular to subcircular pores and rough surface. Two primary radial polar spines (which extend as internal beams joining the two shells) joined distally by a circular ring. Cortical shell diameter without spines: 70-80 µm. Ref: Nigrini (1967).
	Spongodictyon spongiosum (Müller) (Figure 15.57) [=Dictyosoma spongiosum]. Generally similar to Spongoplegma rugosa, except that center hosts a double medullary shell; second medullary shell usually incompletely developed. Outermost shell diameter: 200 µm. Ref: Müller (1858).
	Spongoplegma antarcticum Haeckel (Figure 15.51). Spongy mass with a single irregular, sponge-like medullary shell in the center. Outer shell diameter: ca. 150 µm. Ref: Boltovskoy and Riedel (1980).
	Spongoplegma rugosa Hollande and Enjumet (Figure 15.52). Spongy mass with a single latticed medullary shell in the center (not focused in the illustration); spongy meshwork is looser toward the periphery of the shell. Outer shell diameter: ca. 300 µm. Ref: Hollande and Enjumet (1960).
	Spongosphaera streptacantha Haeckel (Figure 15.59) [= ?Rhizoplegma boreale]. Two concentric, spherical, latticed medullary shells and one spongy cortical shell. With large, three-bladed spines with serrated edges originating in the second medullary shell and protruding conspicuously outside of the spongy outermost shell. Outer shell diameter without spines: ca. 300 µm. Ref: Hollande and Enjumet (1960).
	Stylatractus spp. group (Figure 2A; 15.35). [= ?Stylatractus, ?Axoprunum, ?Stylosphaera, ?Xiphosphaera, ?Lithatractus, ?Xiphatractus]. Usually two latticed shells, outermost spherical to oval-shaped, often thick-walled with irregular pores; medullary shell spherical. Two polar spines of equal or different size, with or without secondary spines. Two-spined and usually two-shelled actinommids comprise a large, sometimes abundant, highly variable and very poorly studied group. Outer shell diameter without spines: 100-150 µm. Ref: Nigrini and Moore (1979).
	Stylosphaera melpomene Haeckel (Figure 15.34) [=Stylacontarium bispiculum]. Two or three (?) latticed shells, outermost with characteristically sub-quadrangular outline, moderately thick-walled, thorny, with irregularly shaped pores; medullary shell spherical. Six stout beams join the two shells; usually two of these beams protrude outside as short, three-bladed polar spines, but the other two pairs may also extend slightly beyond the cortical shell-wall. Polar spines of equal or different size. Outermost shell diameter without spines: 80-130 µm. Ref: Benson (1966).
	Styptosphaera spumacea Haeckel (Figure 15.50). Shell is an irregular spongy mass without central cavity. Shell diameter: ca. 450 µm. Ref: Boltovskoy and Jankilevich (1985).
	Thecosphaera inermis (Haeckel) (Figure 15.38). Three concentric latticed shells; pores on outermost relatively small, circular, regularly arranged, without frames (in some specimens frames around the pores can develop, in which case this species merges with Actinomma sol). Cortical shell usually smooth, barren of spines. Cortical shell diameter: ca. 80 µm. Ref: Boltovskoy and Riedel (1980).