1164 THE VOYAGE OF H.M.S. CHALLENGER. 



3. Litharachnium arachnodiscus, Haeckel. 



Litharachnium arachnodiscus, Haeckel, 1862, Monogr. d. Badiol., p. 283, 



Carpocanium arachnodiscus, EErenberg, 1861, Monatsber. d. k. preuss. Akad. d. Wiss. Berlin, 

 p. 296 ; Abhandl. d. k. Akad. d. Wiss. Berlin, 1872, Taf. ii. fig. 8. 



Shell flatly campanulate, nearly discoidal, with convex (?) lateral outlines. Apex with three 

 unequal cortinal pores. Nine stronger radial primary ribs complete; between them numerous 

 secondary intercalated ribs (sixty to seventy). Margin ciliate. 



Dimensions. Shell O03 long, 01 broad (?). 



Habitat. Arctic Ocean (between Greenland and Iceland), depth 1000 fathoms (Schaffner),. 



4. Litharachnium epeira, n. sp. (PL 55, fig. 9). 



Shell flatly conical or tent-shaped, with concave lateral outlines. Apex with three unequal 

 cortinar pores. Twelve stronger radial primary ribs complete ; between them numerous (twenty- 

 four to thirty-six) thinner secondary, and very numerous (more than one hundred) tertiary ribs. 

 Margin reflexed, like the curved brim of a hat. 



Dimensions. Shell 012 long,, - 27 broad.. 



Habitat. Central Pacific, Station 274, surface. 



Subgenus 2. Litharachnoma, Haeckel. 



Definition. Apex with four cortinar pores (two anterior jugular' and two posterior 

 cardinal pores). 



5. Litharachnium discoides, n. sp. 



Shell flat, funnel-shaped, nearly discoidal, with concave outlines. Apex with four unequal 

 cortinar pores (two smaller jugular and two larger cardinal pores). Twelve strong primary or 

 perradial ribs alternating with twelve weaker secondary or interradial ribs ; between these there are 

 twenty-four shorter tertiary or adradial ribs, and in the outer flat, discoidal, half of the shell very 

 numerous peripheral radial ribs (more than two hundred to three hundred). Margin flat, discoidal. 



Dimensions. Shell about 0'2 long, 112 broad. 



Habitat. Equatorial Atlantic, Station 34*7, surface. 



6. Litharachnium pilidium, n. sp. 



Shell flat, hat-shaped, with S-shaped outlines, in the upper half convex, in the lower half 

 concave. Apex with four equal crossed cortinar pores. Thirty primary ribs of equal size; four of 

 them are the prolongations of the four cortinar beams, eight intercalate between these secondary, 



