REPORT ON THE RADIOLARIA. 1697 



inflated distal apex a trident or fusciua, similar to that of Circoporus sexfusdnus (PI. 115, fig. 2). 

 Mouth with nine convergent, conical, denticulate teeth (fig. Za). 



Dimensions. — Diameter of the shell 0-6, length of the spines 0'4. 



Habitat. — South Atlantic, Station 318 (east of Patagonia), depth 2040 fathoms. 



3. Ctrcospathis tetradeca, n. sp. 



Shell spherical, covered with irregular, polygonal plates. Nine radial spines, cylindrical, as long 

 as the radius of the shell, bristly, armed at the distal apex with a trident. (In one specimen six 

 spines possessed three terminal branches, two spines two branches, and one spine four branches.) 

 The broader base of each spine is surrounded by a corona of nine pores and a circle of curved 

 bristles. Mouth with nine smooth conical teeth. 



Dimensions. — Diameter of the shell 0"55, length of the spines 0'3. 



Habitat. — South Atlantic, Station 332 (west of Tristan da Cunha), depth 2200 fathoms. 



4. Circosjmthis tctrodonta, n. sp. (PI. 115, fig. 10). 



Shell subspherical or polyhedral, with fourteen triangular, convex faces, covered with irregular 

 polygonal plates. Nine radial spines cylindrical, nearly smooth, about as long as the diameter of 

 the shell ; at the distal apex with four strong curved horns, like those of Circoporics hexastylus, 

 PI. 117, fig. 4. Each spine is surrounded at the base by a corona of nine irregular pores. Mouth 

 with four large, prominent, conical teeth, which are spinulate, with vertical inner edge (fig. 10). 



Dimensions. — Diameter of the shell O'o, length of the spines 0'45. 



Habitat. — South Atlantic, Station 323 (east of Buenos Ayres), depth 1900 fathoms. 



Genus 713. Circogonia,^ n. gen. 



Definition. — C ircoporida with a regular icosahedral shell, composed of twenty 

 congruent, triangular plates, witji twelve corners, from which arise twelve radial spines. 



The genus Circogonia is remarkable for the regular icosahedral form of its shell, a 

 geometrical fundamental form, which occui's very rarely in organised bodies (as in 

 Aidacantha icosahedra, and in some Astrosphserida with twelve regularly disposed 

 radial spines). The shell is composed of twenty triangular, equilateral and congruent 

 plates, which are sometimes sej)arated by prominent crests ; their surface is panelled by 

 smaller hexagonal or polygonal secondary plates. The thirty edges between the plates 

 are sometimes thickened. From the twelve corners of the regular icosahedron (where 

 every five triangular plates meet), twelve equal radial spines arise, each of which is 

 surrounded at the base by a corona of nine to sixteen pores. Two sjjecies only of 

 Circogonia have been observed; the one has smooth spines, forked at the distal end, 



1 Circogonia = Polyhedron witli circles of pores ; x.i^ko;, -/ml*. 

 (ZOOL. CHALL. EXP. — PAET XL. — 1886.) Er 213 



