Order Nassellaria

Family Plagoniidae

	Antarctissa spp. group? (Figure 3D, 15.104) [=?Antarctissa strelkovi, ?Antarctissa longa]. Shell outline triangular to oval, cephalis partly submerged into thorax. Shell-wall thick. A. strelkovi (Figure 3D) and A. longa differ from A. denticulata by having thinner and spinier shell-walls. Shell height: 100-160 µm. Ref: Petrushevskaya (1967).
	Arachnocorys circumtexta Haeckel (Figure 15.110). Spherical cephalis provided with numerous spines; those directed upwards are interconnected by a spider web-like lattice of very thin bars; the ones directed toward the base support an incipient thorax formed by a coarser lattice with irregular pores, with several very large pores located in the neck area. Overall shell height: ca. 140 µm. Ref: Petrushevskaya (1971a).
	Callimitra carolotae Haeckel (Figure 15.123). The small, dome-shaped cephalis is provided with very long apical (directed upwards), dorsal and main lateral spines (directed down and sideways) interconnected by a delicate meshwork which forms three basal plates and three lateral plates. Overall shell height: ca. 200 µm. Ref: Haeckel (1887).
	Clathrocanium coarctatum Ehrenberg (Figure 15.114). Cephalis with a large, three-bladed apical horn which may have lateral thread-like, anastomosing pojections. The dorsal and two main lateral spines, directed down and sideways, are joined by narrow lattice plates which form a small thorax. Overall shell height: ca. 100 µm. Ref: Petrushevskaya (1971a).
	Clathrocorys teuscheri Haeckel (Figure 2G; 15.112). Similar to C. coaerctatum, except that the apical, dorsal and main lateral spines are joined by a well-developed lattice. Overall shell height: ca. 150-190 µm. Ref: Petrushevskaya (1971a).
	Helotholus histricosa Jorgensen (Figure 15.113). Spiny, dome-shaped shell. Cephalis merging smoothly with thorax; thorax with large and irregular pores, without defined termination. Maximum shell width: ca. 100-120 µm. Ref: Petrushevskaya (1971a).
	Lampromitra coronata Haeckel (Figure 15.115). Shell in the shape of a Chinese peasant hat. Thorax with subregular circular pores increasing in size slightly towards the base, with a well defined peristome of a row of small pores and minute spines. Shell diameter: ca. 200 µm. Ref: Petrushevskaya (1971a).
	Lampromitra danaes (Haeckel) (Figure 15.116) [=Corocalyptra danaes]. Overall shell-shape similar to L. coronata. Pores on thorax regular, polygonal, strongly increasing in size toward its base. Rim of thorax represented by a very regular row of small, rectangular pores followed inmmediately by one of much larger pores. Shell diameter: ca. 180 µm. Ref: Haeckel (1887), as Clathrocyclas danaes.
	Lampromitra quadricuspis Haeckel (Figure 15.117). Generally similar to L. coronata, except that cephalis is more elongate, pores on thorax are larger and its termination is ragged. Shell diameter: 120-350 µm. Ref: Benson (1966).
	Lampromitra schultzei (Haeckel) (Figure 15.118). Similar to L. coronata, except that pores on thorax are considerably larger and less regular. Peristome with two-three rows of regularly aligned, small, subrectangular pores. Shell diameter: ca. 100 µm. Ref: Boltovskoy and Riedel (1980).
	Lophophaena butschlii (Haeckel) (Figure 15.108). Elongated cephalis, the top of which is usually unfinished, short conical thorax. Overall shell height: ca. 100 µm. Ref: Petrushevskaya (1971a).
	Lophophaena hispida (Ehrenberg) (Figure 3I; 15.109). Cephalis spherical, with very large pores and many long, thin spines. Thorax conical, its pores decreasing in size toward the base; sometimes an incipient abdomen present. Overall shell height: ca. 150 µm. Ref: Petrushevskaya (1971a).
	Neosemantis distephanus (Haeckel) (Figure 15.120). Skeleton composed of an oval or pyriform ring (fused main lateral spines) both poles of which are connected by a third bar (the apical spine); from its base protrudes the dorsal spine. All skeletal elements very spiny. Major ring diameter: 70-80 µm. Ref: Petrushevskaya (1971a).
	Peromelissa phalacra (Haeckel) (Figure 15.107) [=Psilomelissa phalacra, Lithomelissa monoceras]. Oval cephalis whose upper part is unperforated or has very few, very small pores. The dorsal and main lateral spines emerge in the neck region as large, three-bladed appendages. Overall shell height: ca. 100 µm. Ref: Petrushevskaya (1971a).
	Phormacantha hystrix (Jorgensen) (Figure 15.111). Cephalis composed of a loose network of arches defining large, irregular pores. Thorax absent. Shell height: 60-70 µm. Ref: Petrushevskaya (1971a).
	Plagoniidae group (Figure 15.105). Includes many generally similar forms with a latticed cephalis and with or without a rudimentary thorax. The systematics of these sometimes extremely abundant forms is confused, and they are generally ignored in most surveys. They include species cited under a variety of generic names, such as Amphiplecta, Arachnocorallium, Arachnocorys, Ceratocyrtis, Dimelissa, Lophophaena, Lophophaenoma, Micromelissa, Peromelissa, Psilomelissa, etc.
	Pseudocubus obeliscus Haeckel (Figure 15.122). Skeleton represented by the sharply three-bladed edges of a 4-sided, truncated pyramid. Shell height: ca. 40 µm. Ref: Petrushevskaya (1971a).
	Sethophormis aurelia Haeckel (Figure 3F; 15.121). Shell in the form of a Chinese peasant hat; cephalis cupola-shaped; thorax with a very delicate, lace-like meshwork of irregular pores decreasing in size toward the periphery and many radial sinuous ribs. Shell diameter: 150-200 µm. Ref: Petrushevskaya (1971a).
	Sethophormis rotula (Haeckel) (Figure 15.124). Central part of spider web-like skeleton is an hexagonal ring whose vertices support 6 radiating spines; three additional radial spines (dorsal and two main lateral) merge in center of hexagon. All spines produce rather regularly spaced anastomosing lateral branches. Diameter of central hexagon: ca. 40 µm. Ref: Petrushevskaya (1971a).
	Tetraplecta pinigera Haeckel (Figure 15.119). Skeleton reduced to four equidistant three-bladed spines arising from a common central point; spines produce thin lateral braches which can anastomose forming a delicate, irregular web. Length of each spine: 25-30 µm. Ref: Haeckel (1887).
	Trisulcus triacanthus Popofsky (Figure 15.106). Small, sparsely perforated cephalis sitting on top of a conspicuously three-lobulated thorax, lobes are most evident in the uppermost part, disappearing gradually toward the base. Shell height: ca. 60 µm. Ref: Petrushevskaya (1971a).