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



to twenty on its half equator. Outer cortical shell thin walled, with irregular, circular pores, only 

 one-third to one-half as large as those of the inner. Distance between the two shells equals the 

 largest diameter of the double lenticular medullary shell. Surface of both cortical shells covered 

 with short conical spines (not longer than the largest pores). 



Dimensions. Mam axis of the external cortical shell 0'2, of the internal 015, of the central 

 capsule 01 ; greatest breadth of the first 014, of the second 01, of the third O'O 1 ? ; pores of the 

 outer shell O'OOl to 0'005, of the inner 0'002 to O'Ol, bars 0'002 to O'OOS ; length of the surface 

 spines 0'005 to O'Ol. 



Habitat. Pacific, central area ; Stations 266 to 274, surface ; Atlantic, Canary Islands (Haeckel), 

 Station 354, surface. 



5. Cypassis halicora, n. sp. 



Internal cortical shell thin walled, with irregular, roundish pores, once to three times as broad as 

 the bars ; ten to eleven on the half meridian of each chamber, fourteen to sixteen on its half 

 equator. Outer cortical shell thin walled, with very delicate network, spindle-like, with conical pro- 

 longations at both poles. Distance between the two shells larger than the greatest diameter of tin- 

 double lenticular medullary shell. Surface of both cortical shells covered with innumerable small 

 thorns. (Resembles closely Cyphocolpus virginis, PI. 40, fig. 11, but without the third shell.) 



Dimensions. Main axis of the external cortical shell 0'21, of the internal 014 ; greatest breadth 

 of the former 013, of the latter 0'09 ; pores 0'003 to 0'009 ; bars of the outer shell O'OOl, of the 

 inner 0'004. 



Habitat. Indian Ocean, Ceylon (Haeckel), surface. 



Genus 158. Cyphocolpus, 1 n. gen. 



Definition. C yphinida with triple cortical shell and double medullary shell, with- 

 out polar spines or tubes. 



The genus Cyphocolpus differs from both foregoing genera by the increased number 

 of the cortical twin-shells. Whilst these are simple in Cyphonium, double in Cypassis, 

 they are triple in Cyphocolpus, composed of three concentric envelopes. The three 

 genera named represent a phylogenetic series, which is repeated in the ontogenetic 

 development of Cyphocolpus. 



1. Cyphocolpus didymus, n. sp. 



Inner cortical shell with circular, subregular pores, twice as broad as the bars; five to six on 

 the half meridian of each chamber, eight to ten on its half equator. Middle cortical shell also 

 with subregular, circular pores of the same size. Outer cortical shell with smooth surface, with 

 more irregular, roundish pores of very different size. The distance between every two shells equals 

 the diameter of the inner medullary shell, which, like the outer, is spheroidal. 



1 Cyphocolpus = Vaulted-bosom ; xi/ipof 



