REPORT ON THE RADIOLARIA. 1287 



The genus Clistoplicena agrees with the preceding Sethophcena in the mouth of the 

 thorax being closed by a lattice-plate. But the appendages of the thorax are terminal 

 feet, not lateral wings; their number is commonly six or nine, rarely more. Clistophcena 

 may be derived either from Tetrahedrina by interpolation of secondary feet between 

 the three primary, or from Sethamphora by development of a basal lattice -plate closing 

 the mouth. 



1. Clistophcena rustiana, n. sp. (PI. 57, fig. 6). 



Shell rough, with distinct collar stricture. Length of the two joints = 3 : 10, breadth = 4 : 11. 

 Cephalis hemispherical, with small, circular pores and a stout oblique horn three times the length, 

 which is three-sided prismatic, and at the top denticulate. Thorax subconical, inflate, with 

 regular, circular, quincuncial pores, increasing in size towards the base. Margin of the flat base, 

 with six divergent, stout feet of the same prismatic form as the cephalic horn, with denticulate 

 distal ends, about as long as the thorax. This elegant species is dedicated to Dr. Exist of Freiburg, 

 the discoverer of numerous fossil Eadiolaria in the Ldassic and Jurassic formations. 



Dimensions. Cephalis 0'03 long, 0'04 broad ; thorax O'l long, O'll broad. 



Habitat. Central Pacific, Station 265, depth 2900 fathoms. 



2. Clistophcena hexolena, n. sp. 



Shell smooth, with slight collar stricture. Length of the two joints = 1:4, breadth = 1:5. 

 Cephalis subspherical, small, with a large, vertical, cylindrical horn, about as long as the shell, 

 and small, circular pores. Thorax nearly three-sided pyramidal or tetrahedral, with three 

 rounded edges and subregular, circular pores. Margin of the flat base with six conical, divergent, 

 straight feet, somewhat shorter than the thorax. (Three on the corners, one on the middle of each 

 side of the triangular base.) 



Dimensions.- Cephalis O'OS diameter, thorax 0'12 long, 0'14 broad. 



Habitat. North Pacific, Station 241, depth 2300 fathoms. 



3. Clistophcena pyramidalis, n. sp. 



Shell smooth, with slight collar stricture. Length of the two joints = 2 : 8, breadth = 3 : 10. 

 Cephalis hemispherical, with a stout pyramidal horn of twice the length. Thorax six-sided 

 pyramidal, with regular, circular pores of equal size, and six prominent, straight edges, which are 

 prolonged into six divergent, pyramidal feet of half the length. 



Dimensions. Cephalis 0'02 long, 0'03 broad ; thorax O'OS long, 01 broad. 



Habitat. Central Pacific, Station 274, depth 2750 fathoms. 



