REPORT ON THE RADIOLARIA. 937 



edges are the lateral halves of the frontal ring, the two other alternate ones are the 

 remaining halves of the reduced sagittal ring (dorsal and ventral rod) (PI. 82, fig. 12). 



In many Tympanida and Coronida a loose irregular lattice or framework is 

 developed, which partly closes the large open gates. But this never reaches the com- 

 pleteness of a true lattice -shell, such as we find in the Spyroidea, Botryodea, 

 and C y r t o i d e a. In by far the greater number of Stephoidea the corners, and 

 partly also the rods, of the shell are armed with numerous irregular spines, often forked 

 or richly branched. Among these spines the descending " basal apophyses " possess 

 a peculiar importance, since by their regular number and disposition they correspond 

 to the radial rods of the Plectoidea, and to the typical " feet " of the Spyroidea 

 and Cyrtoidea. The most important of them are the three cortinar feet (one caudal 

 and two pectoral) of Cortina, Cortiniscus, &c. (compare above, p. 891). 



The Central Capsule exhibits in the Stephoidea the same characteristic 

 structure as in all other MONOPYLEA, first exactly pointed out by Richard Hertwig in 

 1879 (Organismus der Radiol., p. 71, Taf. vii. figs. 4, 5). Its form is commonly ovate 

 or ellipsoidal, sometimes also lentelliptical or nearly spherical. It exhibits constantly 

 on the basal pole the porochora or porous area, and in the basal half the podoconus or 

 pseudopodial cone. From the surrounding sagittal ring it is separated by a thick 

 jelly-like calymma, which commonly exhibits numerous zooxanthellae. The numerous 

 pseudopodia are commonly branched, with rather rare anastomoses. The membrane of 

 the central capsule is thick. 



Synopsis of the Families of Stephoidea. 



I. Skeleton composed of the simple vertical sagittal ring only, without secondary 



rings, . . . . . . . . .1. STEPHANIDA. 



II. Skeleton composed of two crossed rings, a vertical sagittal and a horizontal basal 



ring, ......... 2. SEMANTIDA. 



III. Skeleton composed of two crossed vertical meridional rings (a primary sagittal 



and a secondary frontal ring), commonly also with a horizontal basal ring, . 3. CORONIDA. 



IV. Skeleton composed of two parallel horizontal rings (upper mitral and lower basal 



ring), both connected by a vertical sagittal ring (and often by a vertical frontal 



ring), . . . . . . . . .4. TYMPANIDA. 



Family XLVIII. STEPHANIE A, Haeckel (PI. 81). 



Monostephida, Haeckel, 1881, Prodromus, p. 447. 



Definition. S tephoidea with a simple sagittal ring, without any lattice -work. 



The family Stephanidais the most simple of all Stephoidea, and probably 

 the common ancestral group of this suborder (compare above, p. 933). The skeleton 



(ZOOL. CHALL. EXP. PART XL. 1886.) Rr 118 



