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



it therefore exhibits the same relation to the latter that Spongodrymus bears to 

 Spongiomma. 



1. Spongothamnus furcatus, n. sp. 



Spongy sphere twice as broad as its inner cavity, with very delicate bars, and irregular, dense 

 framework. From the surface arise one hundred and fifty to one hundred and eighty thia, forked, 

 bristle-shaped spines, half as long as the radius ; both fork branches one-third as long as the basal 

 or simple part. 



Dimensions. — Diameter of the sphere 0'3, of its inner cavity 0"15 ; length of the spines 0'08. 



Habitat. — North Pacific, Station 241, surface. 



2. Spongothamnus scoparius, n. sp. 



Spongy sphere four times as broad as its inner cavity, with thick bars and rather loose frame- 

 work. Prom the surface arise sixty to eighty broom-shaped radial spines, as long as the radius, each 

 in the basal half simple, in the distal half with six to twelve irregularly ramified branches (similar 

 to the spines of Cromyodrymiis ahietimis, PI. 30, fig. 6). 



Dimensions. — Diameter of the sphere 0'4, of the inner cavity 01 ; length of the spines 0'2. 



Habitat. — Central Pacific, Station 271, surface. 



Genus 115. Sjyongopila,^ Haeckel, 1881, Prodromus, p. 456. 



Definition. — A s t r o s p h se r i d a with a single, spherical, latticed medullary shell, 

 immediately enveloped by the sj)ongy framework of the cortical shell ; on the surface 

 of the latter are numerous radial spines. 



The genus Spongopila is a Spongoplegma with radial spines. On the other hand 

 it may be derived either from Elaphococcus, by communication of the branched spines, 

 or from Araclinosphcera, by development of spongy branches between the concentric 

 spheres. 



1. Spongopila dichotoma, n. s-p. 



Medullary shell with regular, hexagonal meshes, six times as broad as the bars. From 

 each nodal-point (between every three meshes) arises a bristle-shaped radial spine, which is 

 dichotomously branched. By communication of the neighbouring branches the loose spongy frame- 

 work of the spherical cortical shell is formed, which is four times as broad as the medullary 

 shell. On the surface occur very numerous bristle-shaped radial spines, as long as the diameter 

 of the meduUary sheU. (May be derived from Elaphococcus) 



Dimensions. — Diameter of the spongy cortical sheU 0-3, of the medullary shell O'OS. 



Habitat. — Tropical Atlantic, Station 347, surface. 



' Spon^qpito = Spongy ball; uTroyyo;, itiAof. 



