184 THE VOYAGE OF H.M.S. CHALLENGES. 



15. Hexalonche aspera, n. sp. 



Cortical shell thin walled, three times as broad as the medullary shell, and covered with short 

 conical spines. Pores regular circular, four to six times as broad as the bars ; eight to ten on 

 the radius. Eadial spines conical, about as long as the diameter of the shell.. 



Dimensions. Diameter of the outer shell 012, pores 0'08, bars O'OOlo ; inner shell O04 ; 

 length of the spines 01, basal breadth 0'02. 



Habitat. South Pacific, Station 300, depth 1375 fathoms. 



16. Hexalonche castanella, n. sp. 



Cortical shell thick walled, five times as broad as the medullary shell, and covered with numerous 

 short conical spines. Pores regular circular, twice as broad as the bars ; ten to twelve on the 

 radius. Eadial spines triangular pyramidal, about as long as the radius of the shell. 



Dimensions. Diameter of the outer shell 0'22, pores O'Ol, bars 0'005 ; inner shell - 045 ; 

 length of the spines 012, basal breadth 0'02. 



Habitat. North Atlantic, Station 353, depth 3125 fathoms. 



Subgenus 3. Hexalonchilla, Haeckel. 



Definition. Pores of the cortical shell irregular, of unequal size or form ; surface 

 smooth, without radial by -spines (other than the six main spines). 



17. Hexalonche hexacantha, Haeckel. 



Ilaliomma hexaeanthum, J. Miiller, 1858, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 35, Taf. iv. 



fig. 5. 

 Haliomma hexacanthum, Haeckel, 1862, Monogr. d. Eadiol., p. 430. 



Cortical shell thin walled, smooth, with irregular polygonal pores (commonly hexagonal or 

 pentagonal), two to three times as broad as the bars ; eight to ten on the radius. Medullary 

 shell one quarter as broad, connected with the former by six thin radial beams which are 

 prolonged outside into six triangular pyramidal spines (not quadrangular, as Miiller describes), 

 longer than the radius of the shell. 



Dimensions. Diameter of the outer shell 0'2, pores O'Ol to 0'015, bars - 005 ; inner shell 

 0'05 ; length of the spines 015, basal breadth O'OIS. 



Habitat. Mediterranean (Messina, Nice, Genoa). 



18. Hexalonche geometrica, n. sp. 



Cortical shell thick walled, smooth, with very peculiar geometrical formation of its network, the 

 pores of which are of very different size and form, but highly regular disposition. Each of the six 



