50 



THE VOYAGE OF H.M.S. CHALLENGER. 



mass of different and often very complicated forms is derived ; this order is by far the 

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

 Eadiolaria. 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 Ethmosphserida, Cladococcida, Ommatida, Spongurida, Discida, Lithelida, and 

 Collosphserida. 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 Sphserellaria, according to the different 

 geometrical form of the central capsule and of the latticed shell enveloping it. The 

 first of these, and the common ancestral group of the whole order, is the Sphseroidea, 

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

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

 one axis ; in the Larcoidea lentelliptical, or triaxon-ellipsoid, by different growth of 

 the capsule in three different " dimensive axes." 



Synopsis of the Four Suborders of Sphserellaria. 



,-, , , i i, i \ Shell a simple sphere or a system of con- 



Central capsule spherical. J 101, j 



( centric spheres, . . . . 1. b phaero idea. 



r< i t i IT -11 v j i f Shell a simple ellipsoid or a cylinder with 



Central capsule ellipsoidal or cylindrical. < , , . , . ' ~ T, . , 



( annular transverse constrictions, . . 2. Prunoidea, 



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



Central capsule lentelliptical or triaxon. { She11 a triaxon-ellipsoid, with three different 



( axes, . . . . .4. Larcoidea. 



Suborder I. SPILEROIDEA, Haeckel. 



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

 Sphceridea, E. Hertwig, 1879, Organismus der EadioL, p. 39. 



Definition. SPUMELLARIA 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 allomorphous). Growth 

 of the shell in the three dimensive axes equal. 



The suborder Sphseroidea, the first and most important of the four of the 

 Sphserellaria, comprises those SPUMELLARIA in which the original geometrical 



