THE RADIOLARIA 145 



ORDER 2. Sphaerozoa. 



Colonial forms. 



FAMILY 1. SPHAEROZOIDAE. Both mega- and microspores developed 

 in the same individual. A lattice-shell absent. Selected forms: 

 Collozoum inerme, Norway (Figs. 3, s, and 25) ; C. pelagicum, Shetlands ; 

 Sphaerozoum ovodimare, Faroe Channel. 



FAMILY 2. COLLOSPHAERIDAE. Mega- and microspores in separate 

 individuals. Skeleton, when present, takes the form of a lattice-shell 

 with or without associated spicules. Selected forms : Oollosphaera huxleyi, 

 Mediterranean (Fig. 23) ; Choenicosphaera murrayana, Shetlands. 



This order is treated fully by Brandt in his Monograph (10) and (22). 



ORDER 3. Sphaerellaria. 



SUB-ORDER 1. SPHAEROIDEA. Central capsule and shell (or shells) 

 spherical. Selected forms : Hexalonche philosophica, H., Faroe Channel ; 

 Hexacontium enthacanthium, Jorg. ; H. pachydermum, Jorg., North Sea ; 

 Hexadoras borealis, Clev., North Sea ; Echinomma, leptodermum, Jorg., 

 Norway and Sweden ; Rhizoplegma boreale, Clev., Norway. 



SUB-ORDER 2. PRUNOIDEA. Central capsule and shell elliptical or 

 cylindrical ; often with transverse constrictions. Selected form : Pruno- 

 carpus datura, H., Faroe Channel. 



SUB-ORDER 3. DISCOIDEA. Central capsule and shell discoid or 

 lenticular; often much flattened. Selected forms: Trochodiscus 

 heliodes, Cler., North Sea ; T. echiniscus, H. ; Lethodiscus microporus, H. ; 

 Astrosestrum acanthastrum, H. ; Spongodiscus favus, Ehr., Faroe Channel. 



SUB-ORDER 4. LARCOIDEA. With lentelliptical central capsule and 

 shell. Selected forms : Lithelius minor, North Sea ; L. arborescens, H., 

 Faroe Channel ; Phorticium pylonium, H., Norway and Sweden. 



SUB-ORDER 5. SPHAEROPYLIDKA. With basal or basal and apical 

 pylome (large opening to the shell). See Dreyer (15). 



SUB-CLASS II. ACANTHARIA. 



Radiolaria in which the skeleton is composed neither of the so-called 

 horny acanthin nor of silica, but (in many cases) of strontium sulphate. 

 The central capsule is perforated uniformly or in networks and segregated 

 pores. The skeleton has the form of spicules radiating from a central 

 point within the capsule (Acanthometrida). Rarely a fenestrated 

 extracapsular skeleton is added (Acanthophractida). 



ORDER 1. Acanthometrida. 



SUB-ORDER 1. ACTINELIIDA. With 10-200 radial or diametral spines 

 not arranged according to Miiller's Law (p. 132). 



FAMILY 1. ASTROLOPHIDAE. Spines radiating from a common centre. 

 Genus 1. Adinelius. All spines of equal length and similar shape. A. 

 purpureus, H., Mediterranean. Genus 2. Astrolophus. Spines of unequal 

 length. 



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