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



Dimensions. Eadius of the odd arm 0'2, of the paired arms 0'15 ; distal breadth of the former 

 0'08, basal breadth 0'04 ; breadth of the paired arms 0'04. 

 Habitat. South Atlantic, Station 325, surface. 



4. Chitonastrum dicranodes, n. sp. 



All three arms in the basal half simple, nearly square, in the distal half forked ; branches 

 straight, blunt. Odd arm twice as large as the paired arms ; angle between the latter larger 

 than the angles between them and the odd arm. (The form of the arms resembles Dicranastrum 

 furcatum, PL 47, fig. 2.) 



Dimensions. Eadius of the odd arm 0'24, of the paired arms 012 ; basal breadth 0'06. 



Habitat. North Atlantic, Station 353, surface. 



5. Chitonastrum lyra, n. sp. (PI. 43, fig. 15). 



Didyastrum lyra, Haeckel, 1881, Prodromus et Atlas (pi. xliii. fig. 15). 



All three arms forked and nearly of the same size, but different in form and position. The 

 distance between the branches of the two paired arms is only one-fourth of the distance between them 

 and the odd arm. Each arm in the basal two-thirds is simple, with eleven to twelve transverse 

 septa, in the distal third forked, each branch with four to five transverse septa. The branches of 

 each arm are curved convexly one to another, ending obtusely. The axis of the simple proximal 

 part is straight in the odd arm, in the paired arms curved concavely towards the middle line. In 

 the figured specimen, which I observed living in Portofino (in September 1880), the central chamber 

 of the central disk and the first surrounding ring were filled with the nucleus of the cell ; 

 both external rings were filled (like all chambers of the arms) with pink oil-globules of the red 

 central capsule. From the mantle, enveloping the shell, radiated innumerable fine pseudopodia 

 (much too short in the figure), and between the two paired arms a long " sarcode-flagellum." 



Dimensions. Eadius of each arm 0'16 ; greatest breadth of the odd arm 0'04 ; basal breadth of 

 the paired arms - 02 ; distance of both branches of each arm 0'08. 



Habitat. Mediterranean, Portofino, near Genoa, Haeckel. 



Genus 232. Trigonastrum, 1 n. gen. 



Definition. P orodiscida with three forked, chambered arms, connected by a 

 patagium. (Arms and angles between them either equal or unequal.) 



The genus Trigonastrum differs from the preceding Chitonastrum, its ancestral 

 form, in the development of a patagium between the arms. It bears therefore to the 

 latter the same relation that Euchitonia does to Rhopalastrum. 



1 rnV/cms<rMm=Triangular star; 



