EEPORT ON THE RADIOLARIA. 489 



11. Archidiscus hexathalamus, n. sp. 



Eing irregular, roundish, or hexagonal, connected with the central chamber by six radial beams 

 of unequal increasing length ; therefore all six ring chambers of gradually increasing size 

 (beginning a spiral convolution, original form of some Discospira). 



Dimensions. Diameter of the ring 0'05 to 007, of the central chamber - 014. 



Habitat. South Pacific, Station 300, depth 1375 fathoms. 



Subgenus 6. Circoniscus, Haeckel. 



Definition. Ring with seven or more chambers, separated by seven or more radial 

 beams. 



12. Archidiscus octoniscus, n. sp. 



Eing circular or regular octagonal, connected with the central chamber by eight equidistant 

 radial beams ; therefore eight ring chambers of equal size. (Compare the central part of the disk 

 of Porodiscus guadrigatus, PL 41, fig. 3.) 



Dimensions. Diameter of the ring 0'04, of the central chamber 0'014. 



Habitat. Central Pacific, Station 268, depth 2900 fathoms. 



13. Archidiscus polythalamus, n. sp. 



Eing circular, connected with the central chamber by nine to ten or more radial beams at 

 nearly equal distances. Eing chambers nine to ten, more or less equal, sometimes also eleven to 

 twelve, more different. (This species is very variable, and may perhaps be divided into a number 

 of different " transformistic species.") 



Dimensions. Diameter of the ring 0'04 to 0'06, of the central chamber 0-015. 



Habitat. Central Pacific, Stations 265 to 274, depths 2350 to 2925 fathoms. 



Genus 213. Axodiscus, 1 n. sp. 



Definition. P orodiscida with a simple central chamber, surrounded by one single 

 concentric ring, which is divided by radial beams into two to six or more radial chambers ; 

 margin of the disk armed with radial spines. 



The genus Axodiscus differs from the preceding Archidisctis only in the shape of the 

 margin of the small lenticular disk, which is armed with a variable number of radial 

 spines, indicating certain axes or radii of the shell. If these marginal spines at certain 

 equal distances from the margin branch and their distal ends become united by these 

 branches forming a concentric second ring, the genus passes into Porodiscus. The 

 different number and disposition of the marginal spines are probably very important, 



1 Ax( discus = Disk with ceitiin axes ; &%i;, S/<rxo;. 

 (ZOOL. CHALL. EXP. PART XL. 18S5.) Rr 62 



