REPORT ON THE EADIOLARIA. 1635 



The geuus Aidastrum diU'ers from the preceding Aidoiila, its ancestral form, only 

 in the development of radial spines at the nodal points of the simple lattice-sphere. 

 It exhibits therefore to the latter the same relation as Aulosph(era does to Aularia. 

 But the meshes of the spherical network are constantly triangular in the two latter 

 genera, polygonal in the two former. The different species of Aulastrum are much 

 rarer, and are not so diflercutiatcd as those of the common Aulosphcera. 



1. Aulastrum monoceros, n. sp. 



Eadial tubes siniple, smooth, straight, cylindro-conical, about as long as the smooth tangential 

 tubes or somewhat longer. Meshes of the network irregularly polygonal, the majority usually 

 pentagonal or hexagonal. 



Dimensions. — Diameter of the sphere 3'0 to 4-0, of the meshes O'lo ; breadth of the tubes 

 0-012. 



Habitat. — Tropical Atlantic, Stations 347, 348, depth 2250 to 2450 fathoms. 



2. Aidastrum dichoceros, n. sp. 



Eadial tubes cylindrical, more or less curved, undulate, smooth, twice as long as the smooth 

 tangential tubes, forked at the distal end, with two divergent curved branches. Meshes of the net- 

 work subregular, hexagonal (as in Aulonia hexagonia, PI. Ill, fig. 1), intermingled with single 

 pentagonal and square meshes. 



Dimensions. — Diameter of the sphere 2-0 to 2-5, of the meshes 0-12 to 018 ; breadth of the 

 tubes 0-01. 



Habitat. — Antarctic Ocean, Station 157, depth 1950 fathoms. 



3. Aulastrum dendroceros, n. sp. (PI. Ill, figs. 4o, h, c). 



Eadial tubes cylindrical, straight or slightly curved, thorny, forked at the distal end, two to 

 three times as long as the thorny tangential tubes ; the thorns are short and thin, partly simple, 

 partly in-egularly branched and scattered, arborescent. Meshes of the network irregularly 

 polygonal, the majority pentagonal or tetragonal. 



Dimensions. — Diameter of the sphere 2-4 ; radial tubes 0-2 to 0-3 long, 0-02 broad. 



Habitat. — North Pacific, Station 241 to 244, surface. 



4. Aidastrum triceros, n. sp. (PI. Ill, figs. 3, 3a). 



Eadial tubes cylindrical, straight, smooth, alwut twice as long as the smooth tangential tubes, 

 armed with three divergent curved teeth at the distal end. Meshes subregular, pentagonal, inter- 

 mingled with a small number of tetragonal and hexagonal meshes. 



Dimensions. — Diameter of the sphere 1-2 to I'S ; radial tubes 015 long, O'Ol broad. 



Habitat. — Tropical Atlantic, Station 349, depth 2450 fathoms. 



