34 THE HELIOZOA 



ORDER 3. Chalarothoraca, Hertwig and Lesser. 



Heliozoa with a loose envelope consisting of isolated siliceous or 

 chitinous spicules bound together by a mucilaginous or protoplasmic 

 matrix. 



Heterophrys, Archer (Figs. 2 (3) and 4). A granular envelope containing 

 very delicate and indistinct chitinous spicules. One nucleus and one or more 

 contractile vacuoles. 10-20 p.. Freshwater (or marine ?). Sphaerastrum, 

 Greeff. According to Penard (14) this genus represents a species of 

 Rhaphidiophrys. Elaeorhanis, Greeff. The endoplasm contains a large 

 yellow or brown oil -globule. Envelope with attached sand -grains and 

 diatoms. 50 /*. Freshwater. Lithocolla, F. E. Schultze. No definite 

 oil-globule. Envelope with numerous siliceous bodies, for the most part 

 adventitious diatoms, and amorphic grains. Often united together in 

 colonies by a gelatinous matrix. 38-45 p-. Freshwater and marine. 

 Lithosphaerella, Frenzel. Envelope covered with several layers of sand- 

 grains. Freshwater (Argentine) and marine (Mediterranean). All the 

 genera so far mentioned were placed by Schaudinn (18) and others in the 

 Order Chlamydophora, but were transferred to the Order Ohalarothoraca 

 by Penard. 



The following genera have isolated siliceous skeletal spicules and 

 are regarded as more typical of the Order. Pompholyxophrys, Archer = 

 Hyalolampe, Greeff. Skeleton composed of minute spherical pearls of 

 silex. 40-50 JJL. Freshwater. Pinaciophora, Greeff. Skeleton con- 

 sisting of overlapping circular plates. 50 p.. Freshwater. The genus 

 Pinacocystis, H. and L., which is said to be marine, is closely related to 

 Pinaciophora. Rhaphidiophrys, Greeff (Figs. 2 (4) and 9). Skeleton consist- 

 ing of a number of minute needles, spindles or half-rings arranged loosely, 

 tangentially, and radially in a protoplasmic envelope. This genus con- 

 tains several species and is widely distributed in fresh water. It is 

 often found in colonial groups. Freshwater and marine (A. pelagica, 

 Ostenfeld [13]). Rhaphidocystis, Penard. Spicules of various forms, but 

 always different from those of Rhaphidiophrys, scattered in a protoplasmic 

 envelope. 12-20 /JL. Freshwater. R. simplex = Acanthocystis simplex, 

 Schaudinn. Central Africa. Acanthocystis, Carter (Figs. 2 (5) and 6). 

 The envelope of siliceous spicules apparently continuous, formed of 

 tangential scales apparently touching one another and an armature of 

 radial needles. This genus contains a large number of species, widely 

 distributed in fresh water. Two species, A. italica and A. marina 

 (Ostenfeld), are marine. The genera Cierikowskia, Schaudinn, and 

 Wagnerella, Meresch., from the White Sea, differ from the others in 

 the possession of a stalk. 



ORDER 4. Desmothoraca, Hertwig and Lesser. 



Heliozoa provided with a continuous basket-like skeleton perforated 

 by holes. 



Clathrulina, Cienkowski (Fig. 2 (2)). Apertures in skeleton relatively 

 large. Provided with a stalk. 70 /z. Freshwater. Hedriocystis, H. 



