_Litharachnium arachnodiscus_, Haeckel, 1862, Monogr. d. Radiol., p. 283. _Carpocanium arachnodiscus_, Ehrenberg, 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 0.03 long, 0.1 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 0.12 long, 0.27 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, 1.12 broad. _Habitat._--Equatorial Atlantic, Station 347, 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, {1165}and the other eighteen tertiary. Between them very numerous peripheral beams. Margin broad horizontal, reflexed like the brim of a "Bismarck" hat. _Dimensions._--Shell 0.17 long, 0.38 broad. _Habitat._--South Pacific, Station 298, depth 2225 fathoms. Genus 515. _Cladarachnium_,[132] Haeckel, 1881, Prodromus, p. 430. _Definition._--#Archiphormida# (vel Monocyrtida multiradiata aperta) with flatly conical, tent-shaped or nearly discoidal shell, and numerous branched radial beams. The genus _Cladarachnium_ differs from the preceding _Litharachnium_ only in the ramification of the radial beams, the distal ends of which project over the margin of the shell. Only one species of the genus has been observed.