PHYLUM PROTOZOA 41 



Typical genera: Haliornma, Ehr., 1838; Actinomma, Haeckel, 1862. 



Order 4. PRUNOIDA. Haeckel recognizes seven families. With spheroidal, 

 ellipsoidal to cylindrical skeleton, single or concentric, sometimes constricted. 



Typical genera: Ellipsidium, Haeck., 1887; Druppula, Haeck., 1887. 



Order 5. DISCOIDA. Haeckel recognizes six families. The skeleton and central 

 capsule are discoidal to lenticular. 



Typical genera: Cenodiscus, Haeck., 1887; Heliodiscus, Haeck., 1887. 



Order 6. LARCOIDA. Haeckel recognizes nine families. The skeleton is ellip- 

 soidal with asymmetrical axes, in some cases forming almost a spiral. 



Typical genera: Larcarium, Haeck., 1887, Pylonium, Haeck., 1881. 



Order 7. SPHEROPYLIDA (Dreyer). Peripylea having in addition to the distrib- 

 uted pores one basal or a basal and an apical opening to the central capsule. 



Typical genus: Spheropyle, Dreyer, 1888. 



Legion 2. Actipylea (Acantharia). Porulose forms in which the pores are aggre- 

 gated in definite areas; the skeleton usually consists of twenty spines of 

 acanthin radiating from the centre of the organism in a regular order (Miil- 

 lerian law). Branches from these spines may unite to form a latticed shell. 



Order S. ACTINELLIDA. Haeckel recognizes three families. The radial spines are 

 more numerous than twenty. 



Typical genus: Xiphacantha, Haeckel, 1862. 



Order 9. ACANTHONIDA. Haeckel recognizes three families. The twenty spines 

 are arranged in regular order (four equatorial, eight tropical, and eight polar), 

 all are equal in size. 



Typical genus: Acanthometron, Miiller, 1855. 



Order 10. SPHEROPHRACTA. Haeckel recognizes three families. With twenty 

 equal, quadrangular spines and a complete fenestrated shell. 



Typical genus: Dorataspis, Haeckel, I860. 



Order 11. PRUNOPHRACTA. Haeckel recognizes three families. The twenty 

 radial spines are unequal, and an ellipsoidal, lenticular, or doubly conical shell 

 is present. 



Typical genus: Thoracaspis, Haeck., 1860. 



Division B. Osculosa. Radiolaria with monaxonic form and with the pores of the 

 central capsule limited to an area on the base, or to one such primary basal 

 area and two secondary, apical areas; these perforated areas of the central 

 capsule are termed oscula. 



Legion 3. Monopylea (Nassellaria). The central capsule is subspherical to ovoid, 

 consists of a single layer of chitin, and is perforated only at one pole. The 

 skeleton is silicious. 



Order 12. NASSOIDA. Haeckel recognizes only one family. Skeleton absent. 



Typical genus: Nassella, Haeck., 1887. 



Order 13. PLECTOIDA. Haeckel recognizes two families. A complete latticed 

 shell is never formed, the skeleton consisting of three or more spines radiating 

 from one point below the central capsule or from a central rod. 



Typical genus: Triplecta, Haeck., 1881. 



Order 14. STEPHOIDA. Haeckel recognizes four families. The skeleton consists 

 of fused spines forming one or more rings. 



Typical genus: Lithocircus, Miiller, 1856. 



Order 15. SPYROIDA. Haeckel recognizes four families. The skeleton consists of 

 a sagittal ring and a latticed shell furrowed in the sagittal plane; in some 

 cases a lower chamber is added to the shell. 



Typical genus: Dictyospiris, Ehr., 1S47. 



Order 16. BOTRYOIDA. Haeckel recognizes three families. Skeleton similar to 

 the preceding, but having in addition one more wing-like process or lobe 

 and one or more additional chambers. 



Typical genus: Lithobotrys, Ehr., 1844. 



