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



Subgenus 2. Diploconium, Haeckel. 



Definition. Mantle of the double cone compressed from both poles of the 

 shortened geotomical axis ; its transverse section therefore elliptical. 



4. Diploconus fasces, Haeckel. 



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

 Diploconus fasces, R. Hertwig, 1879, Organismus d. Radiol., p. 28, Taf. ii. fig. 3. 



Mantle of the double cone compressed, with elliptical transverse section ; its contour straight ; 

 its surface with numerous longitudinal furrows ; its margin finely denticulated. Diameter 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 than their conical sheath, four-edged. The eighteen smaller 

 spines thick and short, cylindrical or a little compressed. 



Dimensions. Length of the shell 018 ; equatorial breadth O025, polar breadth 0'07. 



Habitat. Mediterranean (Messina), surface. 



5. Diploconus cotyliscus, n. sp. (PL 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 015. 



Habitat. Tropical Atlantic, Station 347, surface. 



6. Diploconus saturmis, Haeckel. 



Diploconus saturnus, Haeckel, 1879, Natiirl. Schopfungsgesch., 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. (Resembles a sheaf.) 



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



Habitat. South Pacific, Station 300, surface. 



7. Diploconus hexaphyllus, n. sp. (PL 140, fig. 2). 



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

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



