1574 THE VOYAGE OF H.M.S. CHALLENGER. 



The genus Aulactinium differs from all the other Aulacanthida in the complete 

 absence of the characteristic fine tangential needles, which constitute in the latter an 

 arachnoidal veil or mantle around the spherical calymma. We accordingly divide 

 the whole family into two subfamilies, the Aulactinida with a naked calymma, and the 

 Aulagraphida with a veil of tangential needles. The radial tubes possess in the 

 few species of Aulactinium observed a very simple shape, as in the closely allied 

 Aulacantha. 



1. Aulactinium actinastrum, n. sp. (PI. 101, figs. 6, 7). 



Eadial tubes slenderly spindle-shaped, slightly curved, gradually tapering from the middle towards 

 both ends. The proximal two-thirds of the tubes enclosed in the calymma are smooth ; the distal 

 freely prominent third is armed with six to eight equidistant verticils of small conical teeth (ten to 

 fifteen in each verticil). 



Dimensions. — Length of the tubes 0"5 to 1'5, breadth 0'02. 



Habitat. — South Pacific, Station 289, depth 2550 fathoms. 



2. Aulactinium actinelium, n. sp. (PL 101, fig. 8). 



Eadial tubes cylindrical, straight, slightly tapering towards both ends. Proximal two-thirds 

 smooth, the distal third studded with numerous small recurved thorns. 

 Dimensions. — Length of the tubes 0'6 to 0'9, breadth 0'02. 

 Habitat. — South Pacific, Station 293, depth 2025 fathoms. 



3. Aulactinium actinosphcerium, n. sp. 



Eadial' tubes cylindrical, straight, smooth, of nearly equal breadth throughout their whole length, 

 without thorns and spathillffi, pointed at both ends. 



Dimensions. — Length of the tubes 1'6 to 2'2, breadth 0'02 to 0'03. 

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



Subfamily 2. Aulogeaphida, Haeckel. 



Definition. — A ulacanthida with an external veil of interwoven, very numerous 

 and thin, hollow, tangential needles, entii-ely covering the surface of the calymma. 



Genus 666. Aulacantha,^ Haeckel, 1860, Monatsber. d. k. preuss. Akad. d. 



Wiss. Berlin, p. 799. 



Definition. — A ulacanthida with a veil of tangential needles, and with simple 

 radial tubes, which bear neither lateral nor terminal branches. 



^ Aulacantha = Txi.hxda,T ST^ine ; eiv'Kos, dxxuSa. 



