EEPORT ON THE RADIOLARIA. 41 



Subgenus 1. Sphcerozonactis, Haeckel. 



Definition. Spicula radiate, not geminate, consisting of three, four, or more needles 

 or shanks, radiating in different directions from one common central point. 



1. Sphcerozoum triactinium, n. sp. 



Spicula all (or nearly all) triradiate, composed of three (or sometimes in few spicula four) needle- 

 like shanks, diverging from one common point. Shanks straight or somewhat curved, smooth, 

 pointed. Central capsules spherical, with one central oil-vesicle. This species may be regarded 

 as the social form of Thalassoxanthium triactinium. 



Dimensions. Diameter of the central capsules 01 to 012, length of the spicula-shanks - 05 



to 01. 



i 



Habitat. South Pacific, Station 295, surface. 



2. Sphcerozoum medusinum, n. sp. 



Spicula all (or nearly all) quadriradiate, composed of four (or sometimes in few spicula three) 

 needle-like shanks (mostly of unequal length), diverging from one common point. Shanks slightly 

 curved, pointed, thorny, covered with small spinules. Central capsules ellipsoidal, containing 

 several (four to eight) oil-vesicles. This species may be regarded as the social form of the solitary 

 Thalassoxanthium medusinum (PI. 2, fig. 5). 



Dimenswns. Diameter of the central capsules 015 to 018, length of the spicula-shanks 0'08 

 to 012. 



Habitat. North Pacific, Station 236, surface. 



3. Sphcerozoum hamatum, n. sp. 



Spicula all (or nearly all) quadriradiate, composed of four (or sometimes in few spicula three) 

 needle-like shanks, mostly of very different size, diverging from one common point. Shanks 

 strong, straight, curved, or hook-like ; thorny, covered with small spiuules on the distal extremity. 

 Central capsules ellipsoidal, large, containing many (ten to twenty) oil-globules. This large species 

 is distinguished by the very irregular form and size of the spicula. 



Dimenswns. Diameter of the central capsules 0'2 to 0'25, length of the spicula-shanks 012 

 to 018. 



Habitat. Central Pacific, Station 265, surface. 



4. Sphcerozoum hexactinium, n. sp. 



Spicula all (or nearly all) hexaradiate, composed of six (or sometimes in few spicula five or 

 seven) needle-like shanks, mostly of equal size, diverging from one common point in two opposite 

 hemispheres (three needles upwards, three needles downwards). Shanks somewhat curved, pointed, 



(ZOOL. CHALL. EXP. PART XL. 1885.) Er 6 



