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



Dimensions. — Diameter of the spongy shell 0'75, of its central cavity 015, of the central cube 

 0-02 ; length of the spines 0-9 to 1-2, breadth 0-02. 

 Hahitat. — Tropical Pacific, Station 225, surface. 



Genus 120. Spongosph(^ra,^ Ehrenberg, 1847, Monatsber. d. k. preuss. 

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



Definition. — A s t r o s p h te r i d a with two concentric latticed medullary shells, 

 connected by radial beams; the outer is immediately enveloped by the spongy frame- 

 work, and bears numerous radial spines. 



The genus Spon'gosphcera (in the definition here restricted) differs from Spongo- 

 pila in the double medullary shell, which in the latter is simple ; it exhibits to the 

 latter the same relation that Spongodictyon among the Liosphserida bears to Spongo- 

 p)legnia. The outer meduUary shell of Spjongosp>h(Bra is immediately enveloped by the 

 spongy wicker-work, which everywhere pierces the wall of the central capsule. 



1. Spongosphcera streptacantha, Haeckel. 



SpongospJuera streptacantha, Haeckel, 1862, Monogr. d. Eadiol., p. 455,' Taf. xxvi. figs. 1-3. 



Spongy shell of polyhedric, irregular outline, the framework being prolonged sheath-Kke into the 

 eight to twelve radial spines, which are quite irregularly distributed, very large, three-sided prismatic, 

 witli three serrated, spirally contorted edges ; their length is twice to four tunes as great as the 

 diameter of the spongy body ; they arise with thinner bases from the outer medullary shell, which is 

 three times as broad as the inner, both having roundish pores, twice to four times as broad as the 

 bars ; surface without radial by-spines. 



Dimensions. — Diameter of the spongy shell 0'2 to 0'6, outer medullary shell 0'04 to 0'06, inner 

 0-012 to 0-016. 



Habitat. — Cosmopolitan ; common in all warmer seas, surface. 



2. Spongosphcera polyacantha, J. Miiller. 



Spongosphcera polyacantha, J. Miiller, 1858, AbhandL d. k. Akad. d. Wiss. Berlin, p. 32, 

 Taf. iv. figs. 1-4. 



Spongy shell spherical, with ten to twenty large radial spines, which arise with thinner bases 

 from the medullary shell, and are prominent on the surface at different lengths ; they are three- 

 sided prismatic (not four-sided), with three leaf-shaped straight edges. Whilst the spongy frame- 

 work is much looser than in the preceding species, both medullary shells have nearly the same 

 shape. 



Dimensions. — Diameter of the spongy shell 0-2 to 0-5, outer medullary shell 0-04 to 0-06, 

 inner 0-012 to 0-016. 



Habitat. — Mediterranean (Nice) ; Atlantic, Station 353, surface. 



' Spongosphcera = Spongy sphere ; a-rroyyo;, oOaii^a. 



