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



9. Lithatractus rosetta, n. sp. 



Outer shell thick walled, thorny, with regular network ; meshes circular, funnel-shaped, its 

 outer aperture elegant, rosette-like, with eight to ten incisions (like Stylo&phcera calliape, PL 16, fig. 6); 

 eight to ten meshes on the half equator, three to four times as broad as the bars. Proportion of 

 the longer axis to the shorter = 5:4. Shorter axis equals three times the diameter of the inner 

 spherical shell. Polar spines three-sided pyramidal, about half as long as the shorter axis, as broad 

 at the base as a mesh. 



Dimensions. Longer axis of the cortical shell 015, shorter 012 ; pores 0'02, bars O'OOo ; length 

 of the polar spines 0'05, basal breadth 0'02 ; diameter of the inner shell 0'04. 



Habitat. South-eastern part of the Pacific, Station 302, depth 1450 fathoms. 



Subgenus 3. Lithatractona, Haeckel. 



Definition. Network of the outer shell irregular, with meshes of unequal size or 

 dissimilar form ; surface smooth, without thorns or papillae. 



10. Lithatractus conifer, n. sp. 



Outer shell thin walled, smooth, with irregular, roundish pores, two to four times as broad as 

 the thin bars ; fifteen to twenty on the half equator. Margin of the pores simple. Proportion of 

 the major axis to the miuor = 3:2. Minor axis twice as large as the diameter of the inner 

 spherical shell, the pores of which are also irregular, roundish, but of half the size. Polar spines 

 conical, somewhat shorter than the main axis, on the base two to three times as thick as a large 

 pore. 



Dimensions. Longer axis of the outer shell 015, shorter axis 01 ; pores 0'002 to - 004, 

 bars O'OOl ; diameter of the inner shell - 05 ; length of the polar spines 012, basal breadth 0'012. 



Habitat. South Atlantic, Station 325, surface. 



11. Lithatractus lobatus, n. sp. 



Outer shell thick walled, smooth, with irregular, roundish pores, four to eight times as broad as 

 the bars ; six to eight on the half equator. Margin of the pores lobed, very irregular, bluntly 

 dentate, by five to twenty slight incisions. Proportion of the major axis to the minor very variable, 

 between 3 : 2 and 9 : 8. Diameter of the inner shell also variable, between one-third and one-half of 

 the outer ; pores of the former scarcely half the size of the latter, simple, roundish, or circular. 

 The inner shell is at some parts' quite spherical, at other parts more or less ellipsoidal. Polar spines 

 conical, very variable in size and form, sometimes in the basal half triangular ; they are sometimes 

 somewhat longer than the main axis, at other times considerably shorter ; their basal breadth is 

 occasionally the same as that of the largest pores, sometimes, however, scarcely half as large. This 

 deep-sea species is very common in the central area of the Tropical Pacific (Stations 266 to 272), 

 and occurs also fossil in the Barbados deposits. It is interesting from its great variability, and 

 sometimes constitutes a transitional form to Stylosphcera. 



