Synopsis of the four Subclasses or Legions of Radiolaria.
| A. HOLOTRYPASTA. | B. MEROTRYPASTA. | ||
| Central capsule everywhere perforated by innumerable small pores. | Central capsule with one large main-opening (with or without small accessory openings). | ||
| Fundamental form originally homaxon (spherical or derived from a sphere). | Fundamental form originally monaxon (egg-shaped or perhaps dipleural). | ||
| I. | II. | III. | IV. |
| Spumellaria. | Acantharia. | Nassellaria. | Phæodaria. |
| (Peripylea.) | (Actipylea.) | (Monopylea.) | (Cannopylea.) |
| Wall-pores of the capsule equally disposed. | Wall-pores of the capsule symmetrically disposed. | Main-opening of the capsule with a porous operculum. | Main-opening of the capsule with a short tubule. |
| Skeleton siliceous or wanting. | Skeleton acanthinic (organic). | Skeleton siliceous (rarely wanting). | Skeleton siliceous (rarely wanting). |
| Calymma without phæodium. | Calymma without phæodium. | Calymma without phæodium. | Calymma constantly with a phæodium. |
Legion I. SPUMELLARIA,
vel Peripylea, vel Peripylaria (Pls. 1-50).
Spumellaria (exclusis Spyridinis), Ehrenberg, 1875.
Peripylea (inclusis Thalassicollis et Sphærozois), Hertwig, 1879.
Peripylaria (inclusis Collodariis et Polycyttariis), Haeckel, 1881.
Definition.—Radiolaria with simple membrane of the central capsule, which is everywhere perforated by innumerable very fine pores. Extracapsulum without phæodium. Skeleton wanting or siliceous. Fundamental form originally spherical.
The legion Spumellaria vel Peripylea, in the extent here defined, was constituted by me in 1883 in my paper on Die Ordnungen der Radiolarien.[[2]] I propose to retain for this legion either the name Spumellaria of Ehrenberg (1875) or Peripylea of Hertwig (1879), although both groups have not quite the same extension. We exclude from the Spumellaria the Spyridina (united with them by Ehrenberg) and include the Collodaria. With the Peripylea of Hertwig we unite his Thalassicollea and Sphærozoea. To avoid any confusion it would perhaps be better to name this legion "Peripylaria."
The Spumellaria agree with the Acantharia in the structure of the simple capsule-membrane, which is perforated by numerous small pores (but devoid of the large main opening, which the Nassellaria and Phæodaria possess), whence we unite both the former as Holotrypasta, both the latter as Merotrypasta.