REPORT ON THE RADIOLARIA. 459 



Subfamily 1. Lithocyclida, Haeckel, 1881, Prodromus, p. 458. 



Definition. — C occodiscida with simple circular disk, without any radial 

 appendages of the margin (either solid radial spines or chambered arms). 



Genus 196. LithocycUa} Ehrenberg, 1847, Monatsber. d. k. preuss. Akad. 



d. Wiss. Berlin, p. 54. 



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

 radial appendages. Medullary shell simple. 



The genus Lithocydia is the most simple form of Coccodiscida, and represents 

 the common ancestral form of this family, from which all other genera of it can be 

 derived. The lenticular, biconvex disk is quite simple, composed of a variable number 

 of concentric, circular, chambered rings, which are pierced by radial beams, and which 

 surround the circular lenticular cortical shell or " phacoid shell." The latter contains 

 a simple spherical medullary shell in its centre, and is connected with it by radial 

 beams. The margin of the disk is circular, quite simple, without radial spines or 

 chambered arms. 



1. Lithocydia cingulata, n. sp. 



Phacoid shell (or lenticular porous cortical shell) three times as broad a? the spherical 

 enclosed medullary shell, surrounded by one single chambered girdle or ring (with about forty 

 chambers of equal size, separated by radial beams). Margin of the disk circular, smooth. Pores 

 of the convex covering plates regular, circular ; eight on the radius of the phacoid shell, two on the 

 breadth of the ring. 



Dimensions. — Diameter of the disk (with one ring) 013, of the phacoid shell 0"1, of the medul- 

 lary shell 0-0.33. 



Hahitai. — Western Tropical Pacific, Station 22.5, depth 4475 fathoms. 



2. Lithocydia lenticula, n. sp. (PI. 36, figs. .3, 4). 



Phacoid shell two and a half times as broad as the enclosed medullary shell, surrounded by 

 three chambered girdles of equal size, which are divided by piercing radial beams each into about 

 fifty chambers. Margin of the disk thorny. Pores irregular, roundish ; seven on the radiu? of the 

 phacoid shell, two on the breadth of each girdle. 



Dimensions. — Diameter of the disk (with three girdles) 0'2, of the phacoid shell O'li, of the 

 medullary shell 0-045. 



Habitat. — Pacific, central area, Station 268, depth 2900 fathoms. 



'■ Lithocydia = Circular stone ; \i6t;, Kvx.'Kiiit. 



