250 THE VOYAGE OF H.M.S, CHALLENGEK. 



very numerous, repeatedly dichotomous or irregularly branched, curved by-spines, longer than the 

 diameter of the outer sheU. Eadial main spines with three dentated edges. All parts of the 

 skeleton, the net bars as well as the radial beams and spines, are very elegantly denticulated 

 (fig. U). The central capsule (fig. la) completely distends the inner shell and forces out protuber- 

 ances through all its pores ; in its centre lies a nucleus one-third its size. 



Dimensions. — Diameter of the outer shell 0'25, inner 016. 



Habitat . — Central Pacific, Station 271, surface. 



Genus 100. Astrosiihcera,^ n. gen. 



Definition. — A s t r o s p li a3 r i d a with two extracapsular cortical shells, connected 

 by long, prismatic, radial spines ; inner and outer shell with thin radial by -spines. 



The genus Astrosphcera differs from its ancestral form, Leptosphcera, in the 

 development of radial by -spines on the surface of both shells. 



Subgenus 1. AstrosphcBvdla, Haeckel. 

 Definition — Radial main spines simjsle without lateral branches. 



1. Astrosphcera hexagonalis, n. sp. (PI. 19, fig. 4). 



Inner shell with regular, hexagonal meshes and very thin bars, having a bristle-shaped, short 

 radial by-spine in each hexagon-corner ; outer shell twice as broad, with simple triangular meshes 

 and tliicker bars, bearing one row of simple bristle-shaped, curved, radial by-spines. Eadial main 

 spines with three smooth edges. 



Dimensions. — Diameter of the outer shell 0-32, inner 016. 



Habitat. — South Pacific ("West Patagonia), Station 302, surface. 



2. Astrosph(era splendens, n. sp. 



Inner shell with regular, hexagonal meshes, four times as broad as the bars, and covered with 

 numerous curved, long, bristle-shaped by-spines ; outer shell three times as broad, with simple 

 triangular meshes and thin bars, bearing a row of very long, curved, bristle-shaped by-spines. 

 Eadial main spines with three dentated edges. All parts of the skeleton elegantly denticulated, as 

 in Drymospliara dcndropJwra (PI. 20, fig. 1). 



Dimensions.— DiameteT of outer shell 0'7, inner 0'24. 



Habitat. — Tropical Atlantic, Station 347, surface. 



' .fls(rosp/«era = Star-sphere; oicT^op, a^ttl^x. 



