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



17. Amphilonche acufem, n. sp. 



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

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

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

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



Dimensions. Length of the two major spines 4 3 to 0'5, breadth O'Ol to 0'03 ; length of the 

 eighteen minor spines O08 to 0'2. 



Habitat. Central Pacific, Stations 266 to 274, surface. 



Genus 342. Amphibelone , l Haeckel, 1862, Monogr. d. Radiol., p. 392. 



Definition. A mphilonchida with two unequal principal spines (the frontal 

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



The genus Amphibelone exhibits among the Amphilonchida the same remarkable 

 differentiation 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 in its peculiar form ; commonly one pole of the longitudinal axis is 

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

 equal. 



Subgenus 1. Amphibelonium, Haeckel. 



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

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

 basal leaf-cross. 



1. Amphibelone aciculata, n. sp. 



Two principal spines thick, without edges and wings, the frontal spine short, spindle-shaped, the 

 caudal three to six 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 spindle-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'D to 2'0 ; breadth of 

 both O'Ol ; length of the eighteen smaller spines - 1 to 0'3. 



Habitat. South Atlantic, Station 325, surface. 



1 Amphibelone =W 'ith two opposed needles ; Afttfii, Pfroyr,. 



