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



PI. 46, fig. 1, but differs in the broader arms and the unequal size of both pairs.) I call this 

 species after the great monistic philosopher Beuedictus Spinoza. 



Dimensions. Eadius of the principal arms 0'3, of the lateral arms 016 ; basal breadth O025, 

 distal breadth 0'05. 



Habitat. South Atlantic, Station 333, surface. 



3. Tessarastrum brunonis, n. sp. (PI. 45, fig. 9). 



Histiastrum brunonis, Haeckel, 1881, Prodromus et Atlas (pi. xlv. fig. 9). 



Cross rectangular. Both principal arms of equal size and form, three times as long as broad, each 

 with ten joints, three times as long as the lateral arms, which are nearly square, with four joints. 

 All arms rounded, at their truncated end little broader than at their base. No spines. Patagium 

 complete, envelops the whole shell, and is composed of two parallel lattice-lamellae on each side of 

 the flat disk, which are connected by very fine perpendicular bars. This is shown clearly in fig. 9, 

 PI. 45, where the disk is seen from the edge. I call this species after the great Italian philosopher 

 Giordano Bruno. 



Dimensions. Radius of the principal arms 0'22, of the lateral arms 012 ; basal breadth 0'04, 

 distal breadth 0'05. 



Habitat. South Pacific, Station 285, depth 2375 fathoms. 



Subgenus 2. Tessarostromma, Haeckel. 

 Definition. The two principal arms of different size or form. 



4. Tessarastrum democriti, n. sp. (PI. 45, fig. 7). 



Histiastrum democriti, Haeckel, 1881, Prodromus et Atlas (pi. xlv. fig. 7). 



Cross not rectangular ; the two anterior angles smaller than the two posterior. All four arms 

 club-shaped, twice as broad at their rounded obtuse distal end as at their base, of unequal length. 

 Posterior principal arm one and a fourth times as long as the posterior, and one and two-thirds as 

 Ion" as the lateral arms. Patagium incomplete, enveloping only the basal half of the arms. I 

 call this species after the great Greek philosopher Democritus. 



Dimensions. Eadius of the posterior arm 0'3, of the anterior 0'25, of each lateral arm 0'22 ; 

 basal breadth 0'05, distal breadth 01. 



Habitat. Pacific, central area, Station 271, depth 2425 fathoms. 



Genus 237. Stephanastrum, 1 Ehrenberg, 1847, Monatsber. d. k. preuss. 

 Akad. d. Wiss. Berlin, p. 54. 



Definition. Porodiscida with four simple, undivided, chambered arms, 

 connected on the distal ends by a spongy, square or rhomboidal, patagial girdle (or a 

 patagium with four large, interbrachial openings). Shell either regular or bilateral 

 (with equal or unequal arms). 



