REPORT ON THE RADIOLARIA. 739 



The genus Acanthochiasma, with a small number of common species, comprises the 

 Chiastolida with ten diametral spines, which are loosely crossed in the centre of the body. 

 I could distinguish only four species, two of which are cosmopolitan and very widely 

 distributed. In all four species the diametral spines are quite simple, cylindrical ; only 

 in one species distinguished by a spiral winding or torsion in the middle part, where 

 they are crossed one to another. We derive Acanthochiasma from Acanthometrou by 

 concrescence of every two spines opposite in one axis of the body. 



1. Acanthochiasma krohnii, Haeckel. 



Acanthochiasma krnhnii, Haeckel, 1862, Moiiogr. d. Eadiol., p. 403, Taf. xix. fig. 7. 

 Acanthochiasma Jnvhiiii, R. Hertwig, 1879, Organi.siuus d. Radiol., Taf. ii. fig. 6. 



Spines needle-shaped, cylindrical, very thin and long, of equal breadth in their whole length, 

 distinguished by a high degree of elasticity. Central capsule colourless or yellowish-white, 

 transparent. Granules of the sarcode colourless. 



DimensioxbS. — Length of the spines 0-5 to I'O, breadth 0-001 to 0-002. 



Habitat. — Cosmopohtan; Mediterranean, Atlantic, Indian, Pacific, very common. 



2. Acanthochiasma rubescens, Krohn. 



Aianthoehiasm,a ruJyescens, Haeckel, 1862, Monogr. d. Radiol., p. 403. 



Spines cylindrical, of equal breadth in their whole length, not very elastic, pointed at the 

 two ends. Central capsule intransparent, reddish, with viohn-shaped concretions. Granules of the 

 sarcode red coloured. 



Dimensions. — Length of the spines 0-2 to 0-6, breadth 0-004 to 0-006. 



Ealitat. — Xorth Atlantic, Madeira, Krohn ; Lanzerote, Haeckel. 



3. Acanthochiasma fusiforme , Haeckel. 



Acanthochiasma fiisiforme, Haeckel, 1862, Monogr. d. Radiol., p. 404, Taf. xix. fig. 8. 



Spines spindle-shaped, from the thicker central part thinned towards the two thin conical ends, 

 perfectly straight and smooth, rigid, inelastic. Central capsule non-transparent, brown. 



Dimensions. — Length of the spmes 0-3 to 0-5, breadth in the central part 0-006 to O'OOO. 

 Habitat. — Cosmopohtan ; Mediterranean, Atlantic, Pacific. 



4. Acanthochiasma spirale, n. sp. 



Spines spindle-shaped, tapering from the thicker central part towards the two thin conical ends, 

 rigid, inelastic ; their central part is spirally convoluted in a very peculiar cochlea-like manner, 

 as in Chiastolus amphicopium (PI. 129, figs. 3a, 35). The ten spines are propped one upon another 

 by the central screw. Central capsule dark, opaque. 



Dimensions. — Length of the spines 0-2 to 0-3, breadth of the central spkal part O'Ol. 



Habitat. — Central Pacific, Station 266, surface. 



