REPORT ON THE RADIOLARIA. 747 



3. Zygacantha compressa, Haeckel. 



Acanthometra compressa, Haeckel, 1862, Monogr. d. Kadiol., p. 378, Taf. xviii. figs. 4a, 46. 



Spines in the proximal half compressed, broad lanceolate, four to six times as broad as in the 

 thin cylindrical distal half. Apex simple or short bifid. Base pyramidal, thickened, without leaf- 

 cross. No middle rib. Central capsule opaque, yellowish or reddish-brown. 



Dimensions. Length of the spines 0'3 to 0'5, breadth of the inner half 0'015 to 0-02, of the 

 outer half 0'002 to 0'003. 



Habitat, Mediterranean (Messina) ; Atlantic (Canary Islands), Station 352, surface. 



4. Zygacantha furcata, J. Muller. 



Zygacantha fureata, J. Muller, 1858, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 51, Taf. ix. 



fig. 6. 



Acanthometra furcata, J. Muller, 1856, Monatsber. d. k. preuss. Akad. d. Wiss. Berlin, p. 499. 

 Acanthometra furcata, Haeckel, 1862, Monogr. d. Radiol., p. 380. 



Spines compressed, fork-shaped, divided by two thickened knots into three sections of nearly 

 equal length ; middle section broader than the proximal, but smaller than the distal section, which 

 is cleft by a deep fissure into two long parallel straight branches. Base pyramidal, without leaf- 

 cross. Central capsule purple, with yellow bodies. 



Dimensions. Length of the spines 01 to 015, basal breadth O'OOS to 0'005, distal breadth 

 0-02 to 0-03. 



Habitat. Mediterranean (Cette), J. Muller, surface. 



Subgenus 2. Zygacanthidium, Haeckel. 



Definition. Spines at the central base with a cross of four prominent leaves ; the 

 meeting edges of the neighbouring lamellae so rest one upon another that twenty-two 

 hollow pyramidal compartments are formed (compare p. 721). 



5. Zygacantha dichotoma, Haeckel. 



Zygacantha dichotoma, Haeckel, 1862, Monogr. d. Radiol, p. 381. 



Acanthometra dichotoma, J. Muller, 1858, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 50, Taf. ix. 

 fig. 5. 



Spines compressed, pincer-shaped, cleft nearly throughout their whole length into two thin parallel 

 straight rods or fork branches, which are united only in their middle by a narrow bridge, and at 

 their central base by the pyramidal small central apex ; above this pyramid each rod is divided 

 into two broad triangular leaves, forming a large basal leaf-cross. Central capsule purple, with 

 yellow bodies. 



Dimensions. Length of the spines 01 to 015, breadth O'Ol to 0'02. 



Habitat. Mediterranean (Nice), J. Muller, surface. 



