788 THE VOYAGE Of H.M.S. CHALLENGER. 



17. Amjihilonche aciifera, n. sp. 



Two principal spines thick, four-sided prismatic in the basal half, cylindrical or spindle-shaped 

 in tlie distal half, with simple conical apex. Eighteen smaller spuaes shorter, thin, bristle-shaped 

 or conical on the base. AU twenty spines in the centre perfectly grown together, forming a 

 single piece of acanthin. (Derived from Amphilonche elongatn by central concrescence.) 



Dimensions. — Length of the two major spines 0\3 to O'o, breadth O'Ol to 0'03 ; length of the 

 eighteen minor spines 0-08 to 0-2. 



Hahitat. — Central Pacific, Stations 266 to 274, surface. 



Genus 342. AmjjJiibelone,^ Haeckel, 1862, Monogr. d. Radiol., p. 392. 



Definition. — A m p li il o n c h i da with two unequal principal spines (the frontal 

 spine very different from the caudal spine); the eighteen smaller spines nearly equal. 



The genus Amphihelone exliibits among the Amphilonchida the same remarkable 

 difl'erentiation of the two principal or longitudinal spines, as Zygostaurus among the 

 Quadrilonchida ; the frontal spine differs commonly from the caudal spine not only in 

 its size, but also iu its peculiar form ; commonly one pole of the longitudinal axis is 

 much more strongly developed than the other. The eighteen smaller spines are nearly 

 ec[ual. 



Subgenus 1. Ampltiheloniuin, Haeckel. 



Definition. — All twenty spines separate, but in contact in the centre and resting 

 one against another hj the triangular sides of their pyramidal bases, without a prominent 

 basal leaf-cross. 



1. Amphihelone acicidata, n. sp. 



Two principal s^Dines thick, without edges and wings, the frontal spine short, spindle-shaped, the 

 caudal three to si.x; times as long, cylindrical, both of equal breadth, with simple conical apex and 

 simple pyramidal base, without leaf-cross. Eighteen smaller spines very thin, bristle-shaped, of the 

 same length as the frontal spine. Central capsule cylindrical or spmdle-shaped, enveloping the 

 two principal spines nearly throughout their whole length. 



Dimensions. — Length of the frontal spine 0'2 to 0'4, of the caudal spine I'fl to 2-0 ; breadth of 

 both O'Ol ; length of the eighteen smaller spines O'l to 0"3. 



Hahltid. — South Atlantic, Station 325, surface. 



' Amphihelone = W\\\i two opposed needles ; «^(p/', /3:>io'jh. 



