.50 THE VOYAGE OF H.M.S. CHALLENGER. 



mass of different and often very comjjlicated forms is deiived ; this order is 1 )y far the 

 largest, and in morphological respects the most important and most interesting, of all 

 Radiolaria. It contains not less than twenty-eight different families, three hundred and 

 five genera, and more than sixteen hundred species. 



In my Monograph (1862) seven families appertaining to this group are described 

 — the Ethmosphasrida, Cladococcida, Ommatida, Spongurida, Discida, Lithelida, and 

 CoUospliEerida. The astonishing increase of this group by the detection of a large series 

 of new and interesting forms, and particularly of important connecting forms between 

 very different branches of it, now enables me to give a much better arrangement. I 

 discern now four suborders or sections of S p h a3 r e 1 1 a r i a, according to the different 

 geometrical form of the central caj)sule and of the latticed shell enveloping it. The 

 first of these, and the common ancestral group of the whole order, is the S p h ?e r o i d e a, 

 with spherical capsule ; in the Prunoidea it becomes ellipsoidal or cylindrical by 

 prolongation of one axis ; in the Discoidea lenticular or diseoidal by shortening of 

 one axis ; in the L a r c o i d e a lentelliptical, or triaxon-ellipsoid, by different growth of 

 the capsule in three different " dimensive axes." 



Si/no2:)sis of the Four Suborders of S p h se r e 1 1 a r i a. 



r. J. 1 11-1 f Shell a simple spliere or a system of con- 



Lentral capsule spherical. < j.-, ir.i ■ ^ 



'■ '■ [ centric si^heres, . . . . l.bphaeroidea. 



ri i 1 1 IT -11 V 1 - 1 ( Shell a simple ellipsoid or a cylinder with 



Central capsule ellipsoidal or cylindrical. • , ,' ^ ^ ■ i_- ^ -n • n 



'^ •' ( annular transverse constrictions, . . 2. r^ruuoidea. 



Central capsule lenticular or diseoidal. Shell a biconvex lens or a flat disk, . 3. Discoidea. 



/-,,! iiiir*! i- i Shell a triaxon-ellipsoid, with three different 



Central capsule lentelliijfical or triaxon. < '■ ' j t • i 



^ ' [ axes, . . . . .4. Larcoidea, 



Suborder I. SPH^EOIDEA, Haeckel. 



SphcBToida, Sphceridea, Sphcerida, Haeckel, 1878, Protistenreich, p. 103. 

 Sphceridea, R Hertwig, 1879, Organismus der Radiol., p. 39. 



Definitioyi. — Sptjmellaeia with spherical central capsule (very rarely somewhat 

 modified, or allomorphous) ; with spherical fenestrated siliceous shell (often an endospherical 

 polyhedron, very rarely of more modified, subspherical form or allomorishous). Growth 

 of the shell in the three dimensive axes equal. 



The suborder S p h se r o i d e a, the first and most important of the four of the 

 S p h 86 r e 1 1 a r i a, comjarises those Spumellaria ' in wliich the original geometrical 



