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



Subgenus 2. Dij>loconium, Haeckel. 



Definition. — Mantle of the double cone compressed from l:iotli poles of the 

 shortened geotomical axis ; its transverse section therefore elliptical. 



4. Diploconus fasces, Haeckel. 



Diploconus fasces, Haeokel, 1862, Monogr. d. Radiol., p. 405, Taf. xx. figs. 7, 8. 

 Diploconus fasces, R. Hertwig, 1879, Oi'ganismus d. Radiol., p. "28, Taf. ii. fig. 3. 



Mantle of the double cone compressed, with ellii^tical transverse section ; its contour straight ; 

 its surface with numerous longitudinal furrows ; its margin finely denticulated. iJiameter of its 

 mouth two-fifths as long as the whole shell and three times as broad as its equatorial diameter. 

 The two main spines one-third longer tlian their conical sheatli, four-edged. The eighteen smaller 

 spines tliick and short, cylindrical or a little compressed. 



Dimensions. — Length of the shell 018 ; equatorial breadth 0'025, polar breadth 007. 



Habitat. — Mediterranean (Messina), surface. 



5. Diploconus cotyliscus, u. sp. (PI. 140, fig. 4). 



Mantle of the double cone compressed, thin walled, with elliptical transverse section ; its 

 contour convex ; surface and margin nearly smooth. Diameter of its mouth half as long as the 

 whole shell and twice as long as its equatorial diameter. The two main spines scarcely longer 

 than their hemispherical sheath. The smaller spines conical, straight, nearly of the same length. 



Dimensions. — Length of the shell 0'3 ; equatorial breadth 0"08, polar breadth 045. 



Habitat.- — Tropical Atlantic, Station 347, surface. 



6. Diploconus saturnus, Haeckel. 



Diploconus satumus, Haeckel, 1879, Xatiirl. Scbcipfungsgesch., Aufl. vii. p. 706, Taf. xvi. 

 fig. 11. 



Mantle of the double cone compressed, thick walled, with elliptical transverse section ; its 

 contour convex ; its surface with numerous deep and irregular longitudinal furrows and marginal 

 incisions. Diameter of its mouth one-third as long as the whole shell and twice as broad as its 

 equatorial diameter. The two hydrotomical spines short, scarcely longer than their sheath. The 

 eighteen other spines thin, cylindrical, nearly of the same length, curved. (Eesembles a sheaf.) 



Dimensions. — Length of the shell 0"24 ; equatorial breadth 0'04, polar breadth 0'07. 



Habitat.- — South Pacific, Station 300, surface. 



7. Diplocomis hexaphyllus, n. sp. (PI. 140, lig. 2). 



Mantle of the double cone compressed, tliick walled, with elliptical transverse section ; its 

 contour straight ; surface with six stronger and numerous smaller straight ribs and six marginal 



