REPORT ON THE RADIOLARIA. 795 



Suborder I. SPHiEROPHEACTA, Haeckel. 

 Definition. — Shell spherical, with twenty radial beams of equal size. 



Family XXXIX. Sph^^rocapsida, Haeckel (PI. 133, figs. 7—1 1 ; 



PI. 135, figs. 6-10). 

 SphcBTocapsida, Haeckel, 1881, Prodromus, p. 469. 



Definition. — Acanthaeia with simple spherical porous shell, composed of 

 innumerable very small plates, each of which is pierced by one radial porule. Twenty 

 radial spines of equal size meeting in the centre of the shell and disposed according 

 to the Miillerian law of the Icosacautha, sometimes short and enclosed in the shell, at 

 other times long and piercing it (rarely rudimentary or quite absent). Shell pierced 

 therefore either by twenty larger perspinal pores or by eighty smaller aspinal pores. 

 Central capsule spherical, enclosed in the porous shell. 



The family S p h a3 r o c a p s i d a, founded by me in 1881 for the single genus 

 Sphcerocapsa, represents a very peculiar and remarkable group of the A c a u t h o- 

 p h r a c t a, very different from the five other families of this suborder, and probably 

 derived, independently of them, directly from the A c a n t h o n i d a. Whilst the lattice- 

 shell of the five other families is composed of the meeting Ijranches of lateral apophyses 

 of the twenty spines, and its meshes are all or partly the intervals between these 

 apophyses, in the Sphasrocapsida the spherical shell has quite another structure, and 

 is composed of innumerable small plates (each with one pore) which are secreted on 

 the surface of the spherical caljnnma, independently of the twenty radial spines, 

 which do not possess true apophyses. 



In all Sphserocapsida the structure of the spherical shell is quite peculiar and 

 different from that of all other Eadiolaria. It is composed everywhere of innumeraljle 

 very small plates or aglets, which are connected irregularly like pa^dng-stones, and 

 form a single continuous layer or pavement on the surface of the spherical calymma 

 (PI. 133, fig. 11, a; PI. 135, figs. 8, 10). The small plates or paving-stones, which 

 we will call " aglets," are connected at their meeting edges by a kind of cement, and 

 form together with it a continuous thick capsule of acanthin. The form of the aglets 

 is commonly more or less iiTegular, roundish or polygonal, sometimes longish (PI. 133, 

 fig. 11, a), more rarely it becomes rather regular, hexagonal, square, or roundish 

 (PL 135, fig. 8). Usually all aglets of one and the same individual are of nearly 

 equal size, between O'Ol and 0-02 in diameter, rarely less or more. The outer face of 

 the aglets is more or less concave, so that the elevated meeting edges of the neighbour- 

 ing aglets commonly form together a prominent network of crests (PL 135, figs. 8, 10) ; 

 rarely the meeting edges partly cover one another like squamules (PL 133, fig. 11, a). 



