REPOET ON THE RADIOLARIA. 1563 



The genus Distephamis of Stohr, therefore, is nothing other than the Dictyocha of 

 Ehreuberg. But I think it is more convenient to retain the name Distephanus for those 

 forms of Dictijocha which possess a simple apical mesh surrounded by a ring of lateral 

 meshes, and in which each piece of the skeleton forms a small truncated pyramid. The 

 basal plane of this pyramid is marked by the original basal ring (Mesocena), the truncated 

 upper plane by the parallel apical ring, and the edges of the pyramid by the rising bars 

 which connect both rings. In this sense, so far as the two rings lying in parallel planes 

 are concerned, the term Distephanus is correct (but not in the original sense of Stohr). 

 The number of the rising bars between the two rings varies from four, five, six to eight 

 or more. It seems rather constant in each species, so that all the pieces of the skeleton 

 of one specimen possess either four or six or eight lateral meshes, &c. But sometimes 

 individual irregularities occur. In the majority of species each skeleton-piece is armed 

 with spines. Usually a radial horizontal spine starts centrifugally from each corner of 

 the basal ring, and on the side of this a small tooth or thorn often starts centripetally or 

 downwards. In the twin-pieces, where the two basal rings are united, these teeth catch 

 into one another. In some species upper spines also occur, starting from the corners of 

 the apical ring. The perradial spines of the corners of the basal ring alternate regularly 

 with the interradial ascending bars, which bisect the sides of the ring, as in Dictyocha. 



1. Distephanus crux, Haeckel. 



Dictyocha crux, Ehrenberg, 1840, Monatsber. d. k. preuss. Akad. d. Wise. Berlin, p. 207; 



Mikrogeol., 1854, Taf. xviii. fig. 56, Taf. xx. fig. 46, Taf. sxxiii. Nr. xv. fig. 9. 

 Dictyocha bipartita, Ehrenberg, 1844, loc. cit., p. 79, Taf. xxii. fig. 44. 



Each pileated piece of the skeleton exhibits four pentagonal lateral meshes around one square 

 central mesh, and is composed of two horizontal square rings ; the smaller upper square is connected 

 with the larger lower square by four ascending interradial beams, which start from the corners of the 

 former and bisect the sides of the latter ; from the corners of the basal ring arise four short 

 perradial spines. 



Dimcnsioiis. — Diameter of the basal ring 002 to 0"03, of the apical ring 008. 



Hahitat. — Tropical Atlantic, Station .347, surface ; fossil in Tertiary deposits of the Mediter- 

 ranean (Sicily, Oran). 



2. Distephamis mesophthalmus, Haeckel. 



Dictyocha mesophthalma, Ehrenberg, 1844, Monatsber. d. k. preuss. Akad. d. Wiss. Berlin, 

 p. 80 ; Mikrogeol., 1854, Taf. xxii. fig. 43. 



Each pileated piece of the skeleton exhibits four lateral meshes around the central mesh, and is 

 composed of two parallel horizontal square rings, like those of Disteiihanus cnw, but distinguished 



