748 THE VOYAGE OF H.M.S. CHALLENGEE. 



6. Zygacantha complanata, n. sp. 



Spines compressed, two-edged, linear, of equal breadth throughout their wliole length. Apex bifid. 

 Base thickened, with a large leaf-cross. (Similar to AmpMlonche complanata , but different in the 

 equal size of all twenty spines, which are somewhat broader.) 



Dimensions. — Length of the spines 0'12 to 0-18, breadth 0'002. 



Habitat. — North Pacific, Station 244, surface. 



7. Zygacantha semicompressa, Haeckel. 



Acanilwnietra hemicompressn, Car, 1884, Zool. Anzeiger, p. 94, ■with wooikut. 



Spines in the pro.ximal half compressed, two-edged, linear, three to four times as broad as in 

 the needle-shaped cylindrical distal half. Apex simple. Base pyramidal, with a small leaf-cross. 

 Central capsule transparent. 



Dimensions. — Length of the spines 0"1 to 0'2, breadth in the proximal half 0'02, in the distal 

 half 0006. 



Hahiteit. — Mediterranean (Genoa), Haeckel; Adriatic Sea (Trieste), Czar, surface. 



8. Zygacantha foliacea, n. sp. 



Spines lanceolate, tapering from the broader middle part towards the two ends, with two dentated 

 or serrated edges and a prominent middle rib. Apex simple. Base with a small leaf-cross. The 

 .spines lil^e the leaves of Agave americana. 



Dimensions. — Length of the spines 015 to 0'2, middle breadth 0'02 to 0'03. 



Habitat. — Indian Ocean, near the Island of Socotra, Haeckel. 



Subgenus 3. Zygacanthonium, Haeckel. 



Definition. — Spines in the centime grown perfectly together and foiming a single 

 star-shaped piece of acanthin. 



9. Zygacantha dicopa, Haeckel. 



Astrolitlnuin clicopum, Haeckel, 1862, Monogr. d. Eadiol., p. 400, Taf. xx. llgs. 3, 4. 



Spines compressed, two-edged, linear, of nearly equal breadth throughout their whole length, with a 

 prominent middle rib, which in the distal third is cleft into two divergent teeth, ending in the 

 two corners of the broad, obliquely truncated apex. All twenty spines with their central bases 

 grown together and forming one single piece of acanthin — a star with twenty rays. 



Dimensions. — Length of the spines 012 to 0'2, breadth O'Ol to 0"02. 



Habitat. — Cosmopolitan ; Mediterranean, Atlantic, Pacific, many Stations, surface. 



