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



6. Spongodiscus cycloides, Haeckel. 



Spongodiscus 'cycloides, Haeckel, 1860, Monatsber. d. k. preuss. Akad. d. Wiss. Berlin, p. 843. 

 Spongocyclia cycloides, Haeckel, 1862, Monogr. d. Eadiol., p. 469, Taf. xxviii. fig. 1. 



Spongy disk on both sides plain, in the central part with five to ten concentric, circular rings, 

 in the peripheral part quite irregularly and densely spongy. Meshes twice to four tunes as broad 

 as the bars. 



Dimensions. Diameter of the disk O'l to 0'2, of the meshes 0'003 to O'OOG. 



Habitat. Mediterranean (Messina), North Atlantic (Canary Islands). 



7. Spongodiscus spongocyclia, Haeckel. 



Spongocyclia triangularis, Stohr, 1880, Palseontogr,, vol. xxvi. p. 119, Taf. vii. fig. 5. 



Spongy disk lenticular, in the thicker central part with eleven to twelve circular, concentric 

 rings, in the thinner, peripheral zone irregularly spongy. Meshes twice to four times as broad as 

 the bars. (The triangular form in the specimen figured by Stohr is accidental, produced by the 

 broken margin.) 



Dimensions. Diameter of the disk 0'2 to 03, of the meshes O006 to O'OOS. 



Habitat. Fossil in Tertiary rocks of Barbados (Haeckel) and Sicily (Stohr). 



Subgenus 3. Spongospira, Stohr, 1880, Palasontogr., vol. xxvi. p. 120. 



Definition. Spongy framework of the disk in the inner part with spiral convolu- 

 tions, in the outer part irregular. 



8. Spongodiscus Jlorealis, HaeckeL 



Spongospira florealis, Stohr, 1880, Palaeontogr., vol. xxvi. p. 120, Taf. viL fig. 6. 



Spongy disk lenticular, in the thicker central part with five to six spiral convolutions, in the 

 outer peripheral zone irregularly spongy. No radial beams piercing the framework. Meshes 

 three to four times as broad as the bars. 



Dimensions. Diameter of the disk 0'26, of the meshes 0'006 to O'OOS. 



Habitat. Fossil in Tertiary rocks of Sicily (Grotte), Stohr. 



9. Spongodiscus spiralis, n. sp. 



Spongospira spiralis, Haeckel, 1881, Prodromus. 



Spongy disk on both sides plain, with twelve to sixteen spiral convolutions in the central part, 

 with irregular, spongy framework in the outer part, pierced by numerous interrupted radial beams. 

 Meshes five to six times as broad as the bars. 



Dimensions. Diameter of the disk 0'2 to 0'3, of the meshes O'Ol to 0'012. 



Habitat. Antarctic Ocean, Station 157, depth 1950 fathoms. 



