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



Genus 211. Ecliinactura } n. gen. 



Definition. — Co ccodiscicla with five chambered arms on the margin of the 

 circular or pentagonal disk, connected by a sj^ongy patagium. 



The genus Echinactura differs from the foregoing Pentactura in the patagium 

 between the arms, and bears therefore the same relation to it as Pentinastnim in 

 the Porodiscida does to Pentalastrum. 



1. Echinactura culcita, n. sp. 



Phacoid shell pentagonal, three times as broad as the meduUary shell, with nine pores on its 

 radius. Arms egg-shaped, about as long as the diameter of the phacoid shell, and in the distal part 

 half as broad. The blunt ends of the arms are so connected by the complete patagium that the 

 whole shell becomes a regular pentagonal disk. 



Dimensions. — Diameter of the phacoid shell O'l, of the medullary shell 0-035; length of the 

 arms Oil, basal breadth 0-04, distal breadth 0-06. 



Habitat. — Pacific, central area, Station 266, depth 2750 fathoms. 



2. Echinactura asteriscus, n. sp. 



Phacoid shell twice as broad as the medullary shell, with seven pores on its radius. Arms 

 lanceolate, twice as long as the diameter of the phacoid shell, in the middle part nearly as broad 

 as the latter, at the distal end with a strong conical terminal spine. Patagium incomplete, envelop- 

 ing only the basal half of the arms. 



Dimensions. — Diameter of the phacoid shell 0-09, of the medullary shell 0'045; length of the 

 arms 0'2, gi-eatest breadth 0'08. 



Hahitat. — Pacific, central area, Station 268, depth 2900 fathoms. 



3. Echinactura goniaster, n. ,sp. 



Phacoid shell three times as broad as the medullary .shell, with nine pores on its radius. Arm.s 

 club-shaped, one and a half times as long as the diameter of the phacoid shell, in the cUstal part 

 nearly as broad as the latter, in the basal part one-third as broad; at the end a strong pyramidal 

 spine. Patagium nearly complete, with concave dentated margin between each pair of arms, there- 

 fore the pentagonal disk of the whole shell with concave sides. 



Dimensions. — Diameter of the phacoid shell 0'12, of the medullary shell O'Oi; length of the 

 arms (without terminal spine) OlS, basal breadth 0-04, distal breadth Ol. 



Hahitat. — Pacific, central area, Station 265, depth 2900 fathoms. 



' Echinactira = EcM'ims-\\ke shell with five rays; Ixi"":, dxris. oi^i. 



