THE VOYAGE OF H.M.S. CHALLENGER. 



3. Seihopyramis enneactis, n. sp. (PI. 56, fig. 7). 



Cephalopyramis enneactis, Haeckel, 1881, Prodromus et Atlas, pi. Ivi. fig. 7. 



Shell smooth, slender, pyramidal. Cephalis large, ovate, with pointed apex, nearly hyaline, 

 with very few and small scattered pores. Thorax very slenderly pyramidal, with straight lateral 

 outlines, and nine stout and straight radial beams, which are connected by fifteen to twenty 

 horizontal complete rings. Meshes subregular, square, simple, without secondary network ; their 

 length and breadth equally increasing towards the mouth. 



Dimensions. Cephalis 0'05 long, 0'03 broad ; thorax (with twenty transverse rings) 0'24 long, 

 O'l broad at the mouth. 



Habitat. Central Pacific, Stations 265 to 268, depth 2700 to 2900 fathoms. 



4. Seihopyramis quadrata, n. sp. (PL 54, fig. 2). 



Shell smooth, slenderly pyramidal, very similar in form and structure to the preceding species ; 

 differing from it in the rudimentary cephalis, which is very small, hemispherical, with few small 

 porules. The three internal cortinar bars of the collar stricture are present ; when they become 

 lost this species passes over into Bathrapyramis quadrata (PI. 54, fig. 1). 



Dimensions. Cephalis O'Ol long, 0'02 broad; thorax (with ten transverse rings) 015 long, 

 O'l broad at the mouth. 



Habitat. North Pacific, Station 244, depth 2900 fathoms. 



5. Sethopyramis guadratella, HaeckeL 



Cornutella, quadratella, Ehrenberg, 1875, Abhandl d. k. Akad. d. Wiss. Berlin, p. 68, Taf. ii. 

 fig. 2. 



Litharachnium quadratella, Biitschli, 1882, Zeitschr. f. wiss. Zool., vol. xxxvi. p. 540, Taf. 

 xxxiii. fig. 37. 



Shell smooth, broadly pyramidal. Cephalis ovate, small, blunt, hyaline, with very few and small 

 pores (in the figure of Ehrenberg brdken off). Thorax broadly pyramidal, with straight lateral out- 

 lines, and nine stout and straight radial beams, which are connected by -eight to twelve horizontal 

 complete rings. Meshes in the upper half regular, square, in the lower half broad, rectangular (in 

 the tenth transverse row twice as broad as long). 



Dimensions. Cephalis 0'03 long, 0'02 broad ; thorax (with ten transverse rings) 015 long, 

 015 broad. 



Habitat. Fossil in Barbados. 



6. Sethopyramis trapezoides, .n. sp. 



Shell smooth, broadly pyramidal. Cephalis large, ovate, hyaline, without pores; its collar 

 septum exhibits distinctly the four collar pores (two larger cardinal and two smaller jugular pores). 



