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



Subgenus 2. Cromyommura, Haeckel. 

 Definition. Pores of the outer cortical shell irregular, of different size and form. 



4. Cromyomma perspicuum, n. sp. (PI. 30, fig. 8). 



Cromyosphcera perspicua, Haeckel, 1879, Atlas (pi. xxx. fig. 8). 



Eadial proportion of the four shells = 1 : 2'5 : 6 : 9. Outer cortical shell very thin walled, with 

 thread-like bars, and irregular, polygonal pores ; inner cortical shell with similar pores, but with 

 thicker bars. Both medullary shells with regular, circular pores (the outer three times as broad as 

 the inner). Numerous thin radial beams connect the latter with the former ; other very thin and 

 numerous beams connect the two cortical shells, and are prolonged outside into short bristle- 

 shaped spines (often longer than in the figure). 



Dimensions. Diameter of the four sheUs (A) 018, (B) 012, (C) 0'05, (D) 0'02 ; pores of the 

 outer shell O'Ol to 0'02 ; length of the spines O'Ol to 0'03. 



Habitat. Central Pacific, Station 274, surface. 



5. Cromyomma quadruplex, Haeckel. 



Cromyomma quadruplex, Haeckel, 1862, Monogr. d. Radiol., p. 446. 



Haliomma quadruplex, Ehrenberg, 1854, Monatsber. d. k. preuss. Akad. d. Wiss. Berlin, p. 243. 



Eadial proportion of the four spheres = 1 : 3 : 7 : 10. Outer cortical shell thin walled, irregularly 

 covered with numerous angular spines, as long as the radius. Pores of all four shells irregular, 

 roundish, increasing in size from the first to the fourth. 



Dimensions. Diameter of the four shells (A) 015, (B) 01, (C) 0'045, (D) 0-015; pores of the 

 outer shell O'Ol to 0'02 ; length of the spines 0'07. 



Habitat. North Atlantic, Station 353, depth 2965 fathoms. 



6. Cromyomma macroporum, Stohr. 



Cromyomma macroporum, Stohr, 1880, Palaeontogr., vol. xxvi. p. 95, Taf. iii. fig. 4. 



Radial proportion of the four spheres 1 : 3 : 6 : 9. Outer cortical shell thick walled, densely 

 covered with short conical spines, as long as the diameter of the pores ; the latter are irregular, 

 roundish, or polygonal, larger and smaller alternating. 



Dimensions. Diameter of the four shells (A) 01, (B) O'OGG, (C) 0-033, (D) O'Oll ; pores of 

 the outer shell 0'033 to 0'016, bars O'OOS ; length of the spines O'Ol. 



Habitat. Fossil in the Tertiary rocks of Sicily, Grotte, Stohr. 



7. Cromyomma circumtextum, n. sp (PI. 30, fig. 4). 



Radial proportion of the four spheres = 1:2:5:7. Outer cortical shell very delicate and thin 

 walled, with thread-like bars and large, irregular, polygonal meshes (larger than the innermost shell); 



