REPORT ON THE RADIOLARIA.. 1253 



Genus 560. Sethopyramis, 1 Haeckel, 1881, Prodromus, p. 432 (sensu emendate !) 



Definition. S ethophormida (vel Dicyrtida multiradiata aperta) with nume- 

 rous straight or slightly curved radial ribs in the wall of the pyramidal thorax. Net- 

 work simple. Cephalis commonly without horn. 



The genus Sethopyramis and the four following genera form together a peculiar 

 small group (Sethopyramida), characterised by the slender pyramidal shell, in the wall 

 of which numerous (six to nine or more) radial ribs are enclosed. These ribs may be 

 regarded as the terminal feet of a Calpophcena or Halicalyptra, which become connected 

 by transverse bars. Sethopyramis may be derived also directly from Patagospyris by 

 loss of the primary sagittal ring and reduction of the cephalis. 



Subgenus 1. Sestropyramis, Haeckel. 



Definition. Pyramidal shell with six radial main beams (sometimes also five or 

 seven, as individual varieties). 



1. Sethopyramis scalaris, Haeckel.. 



Carnuidla scalaris, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 68, Taf. ii. fig. 1. 



Shell smooth, slenderly pyramidal, hexagonal. Cephalis large, subglobular, hyaline, without 

 pores (or with very small and scarce pores). Thorax with six straight (or little curved) stout 

 longitudinal ribs or radial beams, which are connected by twenty to thirty complete, hexagonal, 

 horizontal rings. The large meshes so produced are regular, square, their length and breadth 

 equally and gradually increasing towards the mouth. 



Dimensions. Cephalis - 04 diameter ; thorax (with twenty-four transverse rings) 0'4 long, 

 015 broad at the mouth. 



Habitat. Fossil in Barbados. 



2. Sethopyramis hexalactis, n. sp. 



Shell thorny, of the same form as, and similar structure to, the preceding species, but differing 

 in the spiny surface and the smaller subglobular cephalis, which bears small circular pores and an 

 oblique conical horn twice the length. The whole surface is covered with short conical thorns. 



Dimensions.- Cephalis 0'02 diameter ; thorax (with twenty transverse rings) 0'25 long, 01 broad. 



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



Subgenus 2. Cephalopyramis, Haeckel, 1881, Prodromus, p. 432. 



Definition. Pyramidal shell with nine radial main beams (sometimes also eight or 



ten, as individual varieties). 



1 Sethopyramis = Sieve-pyramid ; oqfa, 



