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



1. Stauractura octogona, n. sp. 



Phacoid shell twice as broad as the medullary shell, with eight pores in its radius. Arms nearly- 

 square, little larger than the phacoid shell, with broad truncated distal ends. The corners of the 

 latter are so connected by the complete patagium, that the whole shell forms a regular octagon. 



Dimensions. — Diameter of the phacoid shell 01, of the medullary shell 0-05 ; length of the 

 arms 0'12, distal breadth Oil. 



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



2. Stauractura tetragona, n. sp. 



Phacoid shell three times as broad as the medullary shell, with eleven pores on its radius. 

 Arms club-shaped,- nearly as long as the diameter of the phacoid shell, and one and a half times as 

 long as broad at the distal part ; at the distal end rounded, blunt, without terminal spine. The 

 terminal points of the arms are so connected by a thin, complete patagium, that the whole shell 

 becomes a regular square. 



Dimensions. — Diameter of the phacoid shell 013, of the medullary shell 0-045 ; length of the 

 arms 012, greatest breadth 0-08. 



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



Subgenus 2. Staur actinium, Haeckel. 

 Definition. — Distal end of the arms furnished v-itli a radial spine. 



3. Statiractura medusina, n. sp. 



Phacoid shell two and a half times as broad as the medullary shell, with nine pores on its 

 radius. Arms club-shaped, one and a half times as long as the diameter of the phacoid shell, and 

 in the outer third nearly as broad as the latter, at the base scarcely one-third as broad; their 

 truncated distal end armed with a strong pyramidal terminal spine. Patagimn incomplete, envelop- 

 ing only the basal half of the arms, with three rectiliuear parallel rows of chambers, forming a 

 square. 



Dimensions. — Diameter of the phacoid shell O'l, of the medullary shell 0-04; length of the 

 arms 0-14, greatest breadth O'OS. 



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



4. Stauractura quadrata, n. sp. 



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

 nearly square, about as large as the phacoid shell, with a strong pyramidal terminal spine at 

 the distal end. Patagium complete, between every two arms triangular, with rectilinear parallel 



