REPORT ON THE RADIOLARIA. 1361 



1. Rhopalatractus pentacanthus, n. sp. (PI. 68, fig. 11). 



Shell very thick-walled, with two sharp strictures. Length of the three joints = 1:6:8, 

 breadth = 1:6:7. Cephalis hemispherical, with conical cavity, and a conical horn of twice the 

 length. Thorax subspherical, separated from the abdomen by a deep lumbar stricture, with small, 

 regular, circular, hexagonally-framed pores. Abdomen three-sided prismatic, with three strong, 

 prominent, wing-shaped edges, which are slightly divergent towards the base, and prolonged into 

 three pyramidal feet about as long as the thorax. Pores of the abdomen disposed in longitudinal 

 rows, which are separated by denticulate crests. Abdominal base inversely pyramidal, and prolonged 

 into a very large, cylindrical, basal, axial spine, nearly as long as the whole shell. 



Dimensions. Length of the three joints, a 0'02, b 012, c 015 ; breadth, a 0'03, b Oil, c 014. 



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



2. Rhopalatractus foveolatus, n. sp. (PI. 68, fig. 10). 



Shell slenderly ovate, thick-walled, with rough, dimpled surface. Length of the three joints = 

 1:3:5, breadth = 2:4:4. Cephalis hemispherical, with spherical cavity, and a thick, conical 

 spine of the same length. Thorax subspherical, with subregular, circular pores. Abdomen 

 inversely conical, with larger, irregular, roundish pores, prolonged at the distal end into a 

 cylindrical, axial, basal spine of about half its length. From the middle part of the abdomen arise 

 three lateral, conical feet, which are slightly curved and divergent downwardly, scarcely as long 

 as the basal spine. All five spines are dimpled. 



Dimensions. Length of the three joints, a 0'02, I 0'06, c 01 ; breadth a 0'04, b 0'08, c 0'08. 



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



3. Rhopalatractus fusiformis, n. sp. 



Shell slender, spindle-shaped, nearly of the same form as in the preceding species. Length of 

 the three joints = 1:2:6, breadth = 1:2:2. Cephalis subspherical, with a cylindrical horn three 

 times the length. Pores subregular, circular, of equal breadth in the thorax and in the abdomen, 

 which is prolonged into a cylindrical, axial, basal spine of the same length. From the upper third 

 of the abdomen arise, from a broad triangular base, three conical wings of half the length, divergent 

 and slightly curved inwards. 



Dimensions. Length of the three joints, a 0'025, b O'Oo, c 015 ; breadth, a 0'03, b 0'06, c 0'06. 



Habitat. Central Pacific, Station 263, depth 2650 fathoms. 



4. Rhopalatractus fenestratus, n. sp. (PL 68, fig. 12). 



Dictyatractus fenestratus, Haeckel, 1881, Prodromus et Atlas. 



Shell nearly spindle-shaped, with two distinct strictures. Lengtli of the three joints =1:3:6, 

 breadth = 1:4:4. Cephalis hemispherical, with a large, club-shaped horn, nearly as long as , the 

 abdomen, sulcated by longitudinal ribs, which are elegantly denticulate in the distal half. Thorax 



(ZOOL. CHALL. BXP. PART XL. 1886.) Rr 171 



