SPECIAL MORPHOLOGY AND TAXONOMY OF SARCODINA 321 



Order 3. Chalarothoraca, Hertwig and Lesser.— Body with a gel- 

 atinous mantle containing spicules of silica or with a close-fitting 

 skeleton of spicules, spines or plates. Typical genera: Pomyho- 

 h/.rophri/s, Raphidiophri/s, Pinacocystis, LithicdUa, Acanthocystis, 

 Diplocystis (I^g. 144). 



Order 4. Desmothoraca, Hertwig and Lesser— Body with skeleton 

 shell of one piece j)erforated by numerous openings. Genus: 

 Clathrulina. 



Fig. 144. — Tjtdcs of spicules in Heliozoa, .4, Raphidiophrys pallida with curved 

 silicious spicules; B, Pinaciophora ruhiconda with tangential plates and forked spines; 

 C, Acanthocystis turfacea, with separated plates and forked spines; D, Pinaciophora 

 fluviatilis. (From Calkins after Penard.) 



Stb-C'lass n. RADIOLARIA, Haeckel. 



Broadly stated the Radiolaria are pelagic organisms of the same 

 general type as the Heliozoa but offer many variations from the 

 homaxonic symmetry of the latter. They are exclusively salt- 

 water forms, surface dwelling for the most part, but may be found 

 at great depths of the sea. Pseudo-alveoli are greatly elaborated 

 and form foam-like spheres with radiating axopodia or with soft 

 protoplasmic pseudopodia-like myxopodia, while complex skeletal 

 elements of silica or strontium sulphate afford the greatest variety 

 of structures and designs. 



A typical radiolarian may be conceived by imagining a resistant 

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