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



The genus Spongoplegma may be regarded as a Carposphcera, in which the 

 simple latticed cortical shell is represented by an irregular spongy framework, imme- 

 diately enclosing the simple latticed medullary shell. 



1. Spongoplegma antarcticum, n. sp. 



Cortical shell with loose spongy framework and rough surface, four to six times as broad as 

 the enclosed simple medullary shell. Pores of the latter regular circular, twice as broad as the 

 bars. From its surface arise numerous (forty to fifty or more) short radial beams, which become 

 forked and compose, by communication of lateral branches, the spongy cortical shell 



Dimensions. Diameter of the spongy cortical shell 0'2 to 0'3, of the latticed medullary shell 

 0-05 to 0-06. 



Habitat. Antarctic Ocean, in large number, together with Cromyospkcera antarctica ; in 

 the Diatom ooze of Station 15 1 ? (depth 1950 fathoms). 



Genus 28. Spongodictyon, 1 Haeckel, 1862, Monogr. d. Radiol., p. 459. 



Definition. L iosphserida forming a sphere of spongy framework, which encloses 

 in the centre a double latticed concentric medullary shell. 



The genus Spongodictyon can be regarded as a TJiecosphcera, in which the simple 

 latticed cortical shell is represented by an irregular spongy framework, which imme- 

 diately encloses the double latticed medullary shell. Sometimes this latter appears 

 triple, the inner surface of the spongy cortical shell forming a smooth spherical lattice- 

 plate, separated by an interval from the double medullary shell. 



Subgenus 1. Dictyoplegma, Haeckel, 1862, Monogr. d. Radiol, p. 458. 



Definition. Spongy cortical shell enveloping immediately the double medullary 

 shell. 



1. Spongodictyon spongiosum, Haeckel. 



Didyosoma spongiosum, J. Miiller, 1858, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 31, Taf. ii. 



figs. 9-11. 

 Dictyoplegma spongiosum, Haeckel, 1862, Monogr. d. Radiol., p. 458. 



Spongy framework of the cortical shell loose, with large, polygonal roundish meshes, on an 

 average as large as the double medullary shell, which is immediately enveloped by it. Both con- 

 centric medullary shells with subregular roundish pores, twice as broad as the bars. 



Dimensions. Diameter of the cortical shell 0'2 to 0'3 or more ; of the outer medullary shell 0'03, 

 inner O'Ol. 



Habitat. Mediterranean (French south coast, surface), J. Miiller. 



1 Spongodictyon = Spongy network ; o-zoyyas, tiUrvov. 



