38 THE VOYAGE OF H.M.S. CHALLENGER. 



rod, irregularly bent and curved. (Differs from the similar ITialassoxantMum octoceras, PI. 2, fig- 6, 

 by slender, more curved shanks, and by the voluminous calymma, there entirely wanting.) 



Dimensions. — Diameter of the capsule 0'5, of the nucleus 0"2, of the calymma 3"0. 



Habitat. — South Atlantic, Station 331, surface. 



Subgenus 3. Lampoxanthura, Haeckel. 



Definition. — Spicula of two or three different kinds, simple, radiate, and geminate- 

 radiate mixed. 



4. Lampoxanthium 23cmclora, n. sp. (PI. 2, fig. 1). 



Spicula mixed, of three diflerent kinds — simple, radiate, and geminate-radiate ; all three kinds 

 partly smooth, partly thorny. The simple needles short, thin spindle-shaped, often curved. The 

 radiate spicula commonly with three or four, rarely five or six, unequal rays, straight or curved. 

 The radiate-geminate spicula commonly with three, rarely four, shanks on each end, often different 

 on both ends of the middle rod. The size, number, and form of the irregular spicula are here quite 

 as variable as in the social Rhaphidozomn pandora, of which it is the solitary representative. The 

 wall of the large central capsule is very thick, with evident pore-canals, separated by a clear 

 interval from the coagulated and vacuolated endoplasm, which contains no oil-globules. Nucleus 

 with numerous nucleoli. 



DiTneiisions. — Diameter of the central capsule 0-5 to 0-6, of the nucleus Ol to 0-2, of the 

 calymma 2 to 4 mm. 



Habitat. — North Pacific, Station 244, surface. 



Family IV. S p H je R o z o i d a, Haeckel (PI. 4). 

 Sphcerozoida, Haeckel, 1862, Monogr. d. Eadiol., p. 521. 



Definition. — B e 1 o i d e a sociaHa. 



The family Sphserozoida comprises all associated or colony-forming Radiolaria, 

 which are provided with an imperfect skeleton, composed of numerous solid needles or 

 spicula, scattered around the central capsule in the calymma. The structure and form 

 of this skeleton is quite the same as in the preceding solitary Thalassosphserida, but on 

 the other hand, the structure and form of the colonies and of the included numerous 

 central capsules is the same as in the skeletonless Collozoida. 



The oldest well-known form of Sphserozoida is the common cosmopolitan 

 S2)hcerozoum ijunctatum, probably first observed in 1834 by Meyen, and called 

 Sphcerozoum fuscum, afterwards more accurately described by Huxley in 1851. 



