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



lateral edges of the prism, and arise from its eight corners. Pores regular, circular, three times as 

 broad as the bars ; about fourteen on the half meridian. Proportion of the three axes = 2:3:4. 

 Medullary shell half as long as the cortical shell. 



Dim-ensions. Length of the cortical shell Oil, breadth 0'07, height O05; pores 0'006, 

 bars O002 ; length of the medullary shell O'OG. 



Habitat. Pacific, central area, Station 263, depth 2650 fathoms. 



9. Larnacantha decacantha, n. sp. 



Cortical shell thorny, with ten short and stout, conical, radial spines, two opposite on the 

 poles of the principal axis (as prolongations of inner axial beams), eight others opposite in pairs in 

 two crossed diagonal planes. Pores irregular, roundish, twice to four times as broad as the bars ; 

 about sixteen on the half meridian. Proportion of the three axes = 3 :3 -l 75 :4. Medullary shell 

 about one-third as long as the cortical shell. 



Dimensions. Length of the cortical shell 016, breadth 015, height 012 ; pores O'OOS to 0'016, 

 bars 0'004 ; length of the medullary shell O'OG. 



Habitat. North Atlantic, Station 354, surface. 



10. Larnacantha dodecantha, n. sp. 



Cortical shell nearly smooth, but with twelve strong conical radial spines ; four in the lateral 

 plane opposite in pairs (two on the poles of the principal, and two on the poles of the transverse 

 axis) ; eight others opposite in pairs in two crossed diagonal planes. Pores with a peculiar dis- 

 position : twelve large elliptical pores in two crossed meridian planes (alternating with the twelve 

 spines), separated by bands of irregular small pores. Proportion of the three axes = 1 : T5 : 2. 

 Medullary shell hexagonal, one-third as long as the cortical shell. 



Dimensions. Length of the cortical shell 015, breadth Oil, height 0'08 ; large pores 0'03, 

 small pores 0'005 to O'Ol, bars 0'003 ; length of the medullary shell 0'05. 



Habitat. Pacific, central area, Station 265, depth 2900 fathoms. 



11. Larnacantha drymacantha, n. sp. 



Cortical shell very spiny, on the whole surface covered with a forest of numerous (thirty to 

 fifty or more) large branched spines, about the length of the shell ; each spine with three to nine 

 lateral branches, simple or forked (very similar to Cromyodrymus cibictinus, PI. 30, fig. 6). 

 Pores very irregular, roundish. Proportion of the three axes = 2 : 2'5 : 3. Medullary shell half as 

 long as the cortical shell. 



Dimensions. Length of the cortical shell 016, breadth 013, height 01 ; pores O'OOo to 0'015, 

 bars 0'03 ; length of the medullary shell 0'08. 



Habitat. Pacific, central area, Station 271, depth 2425 fathoms. 



