460 THE VOYAGE OF H.M.S. CHALLENGEE. 



3. Lithocyclia ocellus, Ehrenberg. 



Lithocyclia ocellus, Ehrenberg, 1854, Mikrogeol., Taf. xxxvi. fig. 30; Abhandl. d. k. Akad. d. 

 Wiss. Berlin, 1875, Taf. xxix. fig. 3. 



Thacoid shell three times as broad as the medullary shell, surrounded by numerous (seven to 

 eleven) chambered rings, which are divided by piercing radial beams each into sixty to ninety 

 chambers. Margin of the disk smooth. Pores regular, circular ; nine on the radius of the phacoid 

 shell, one single pore on each chamber. 



Dimensions. Diameter of the disk (with eleven rings) 0'22, of the phacoid shell CM, of the 

 medullary shell 0'035. 



Habitat. Fossil in the rocks of Barbados. 



4. Lithocyclia monococcus, n. sp. 



Stephanopyxis dubiosa (1), Bury, 1862, Polycystins of Barbados, pi. xiii. figs. 1, 2. 



Phacoid shell four times as broad as the medullary shell, surrounded by numerous (five to 

 eight) chambered rings, which are divided by piercing radial beams each into fifty to seventy 

 chambers. Margin of the disk thickened, thorny. Pores regular, circular ; seven on the radius 

 of the phacoid shell, one single pore on each chamber. 



Dimensions. Diameter of the disk (with eight rings) 018, of the phacoid shell 012, of the 

 medullary shell 0'03. 



Habitat. Pacific, central area, Station 267, depth 2*700 fathoms; also fossil in the rocks of 



Barbados. 



5. Lithocyclia heteropora, n. sp. 



Phacoid shell two and a third times as broad as the medullary shell, surrounded by live to 

 nine chambered rings, which are divided by piercing radial beams each into fifty to seventy chambers. 

 Margin of the disk smooth. Pores very different in the inner and outer part of the surface; in the 

 phacoid shell larger, regular, circular, eight on its radius, in the chambered periphery very small and 

 irregular, somewhat spongy. 



Dimensions. Diameter of the disk (with nine rings) 0'2, of the phacoid shell 013, of the 

 medullary shell 0'055. 



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



Genus 197. Coccodiscus, 1 Haeckel, 1862, Monogr. d. Radio!., p. 485. 



Definition. C occodiscida with simple circular margin of the disk, without radial 

 appendages. Medullary shell double. 



The genus Coccodiscus has quite the same form and structure as the preceding 

 Lithocyclia, and differs from it only in the double medullary shell, composed of two 

 concentric latticed spheres ; sometimes the inner medullary shell is spherical, the outer 



1 Coccodiscws=Disk with nucleus ; XO'KXOJ, olax.o;. 



