EEPOET ON THE RADIOLARIA, 889 



Legion III. NASSELLARIA, 



vel Monopylea, vel Monopylaria (Pis. 51-98). 



Nassellaria (inclusis Spj^ridinis), Ehrenberg, 1875. 



Monopylea, Hertwig, 1879. 



Monopylaria, Haeckel, 1881. 



Cyrtida et AcantJwdesmida, Haeckel, 1862. 



Definition. — Radiolaria with simple membrane of the central capsule, which 

 is monaxou or bilateral, and bears on one pole of the main axis a porous area 

 (porochora), forming the base of a peculiar intracapsular cone (podoconus). Extra- 

 capsulum without phseodium. Skeleton siliceous, very rarely wanting. Fundamental 

 form originally monaxon, often dipleuric or bilateral. 



The legion Nassellaria vel Monopylea, in the extent here defined, was constituted 

 in 1879 by Richard Hertwig in his work Der Organismus der Radiolarien 

 (pp. 133—137). He gave to this large group the rank of an order, and united in it the 

 two families Acanthodesmida and Cyrtida, which I had constituted fii'st in 1862 in 

 my Monograph (pp. 237, 265, 272) ; but he added, too, as a third family the 

 Plagiacanthida, united by me with the former. In the first system of Ehrenberg (1847, 

 loc. cit., pp. 53, 54), four families belonging to the Monopylea were enumerated, the 

 Halicalyptrina, Lithochytrina, Eucyrtidina, and Spyridiua. He united the three former 

 under the name " Polycystina solitaria," which he afterwards changed into Nassellaria 

 (1875, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 157). 



In my Monograph of the Radiolaria (1862, pp. 265—345) forty -four genera of 

 Nassellaria were enumerated (six Acanthodesmida and thirty-eight Cyrtida), whilst 

 the total number of genera in the whole class of Radiolaria at that time amounted to 

 one hundred and thirteen. But owing to the astonishing number of new and interesting 

 forms of this legion which I afterwards detected in the collection of the Challenger, 

 in 1881 I distinguished in my Prodromus not less than three hundred and seventeen 

 genera. These were disposed in fi^ve large main groups, retained in the jiresent Report, 

 with twenty-six families, viz., (1) Plectoidea (with three families), (2) Ste- 

 p h o i d e a (with four families), (3) Spyroidea (with four families), (4) Botryodea 

 (with three families), and (5) Cyrtoidea (with twelve families). The first two 

 groups have an incomplete or rudimentary skeleton, and may be united in the order 

 Plectellaria, whilst the other three families possess a complete latticed shell, and 



(ZOOL. CHALL. ESP. PART XL. 1889.) Ef 112 



