REPORT ON THE RADIOLARIA. 1657 



13. Challengeron histerhum, n. sp. 



Shell subcircular, lenticular, strongly compressed, with three stout conical spines on the aboral 

 pole ; the middle spine is placed in the main axis, as long as the radius and three times as long 

 as the two others. Peristome semitulmlar, straight, vertical, about as long as the radius, with three 

 divergent teeth, the middle of which is odd and twice as large as the two paired lateral teeth. 



Dimensions. — Diameter of the shell 022 ; length of the peristome 01. 



Habitat. — Indian Ocean, Madagascar (Rabbe), surface. 



14. Challengeron heptacanthum, n. sp. 



Shell ovate, slightly compressed, with a series of five stout, conical, radial spines on the aboral 

 margin ; the middle spine is placed in the main axis and longer than the radius, twice as long as 

 the two next, and three times as long as the more distant spines. Peristome short and broad, 

 collar-shaped, with two large, divergent, straight teeth, each of which is longer than the sheU-radius 

 and bears at its base a large hole. 



Dimensions. — Length of the shell 0-09 to Oil, breadth 0-07 to 0-08 ; length of the teeth 0-07. 



Heibitat. — Tropical Atlantic, Stations 347, 348, depth 2250 and 2450 fathoms. 



15. Challengeron crosbiei, n. sp. (PI. 99^ fig. 11). 



Shell ovate, strongly compressed, with a series of seven to nine conical spines on the aboral 

 margin ; the middle spine is placed in the main axis, as long as the radius, and much larger than 

 the six or eigjit other spines. Peristome short and broad, collar-like, with several small spines 

 and two slender, widely distant, conical teeth, which are half as long as the shell, and curved 

 towards one another like a pincer, each with a large hole at its base. 



Dimensions. — Length of the shell 0-08 to 0-09, breadth 0-06 to 007 ; length of the two larger 

 teeth 0-04 to 0-05. 



Habiteit. — Central Pacific, Station 270 to 274, depth 2350 to 2925 fathoms. 



16. Challengeron huchanani, n. sp. (PL 99, fig. 12). 



Shell ovate, slightly compressed, with a terminal comb of nine to twelve conical radial spines, 

 densely crowded on the aboral pole ; the middle spine is placed in the main axis, about half as long 

 as the shell and much larger than the others. Peristome subcorneal, semitubular, recurved, half as 

 long as the shell, with five triangular teeth ; the dorsal odd tooth is inclined backwards, the two 

 parallel pairs of lateral teeth directed ventrally. 



Dimensions. — Length of the shell 015 to 018, breadth 01 to 012 ; length of the peristome 

 0-06 to 0-08. 



Hahitat. — Tropical Atlantic, Station 348, depth 2450 fathoms. 



(ZOOL. CHALL. EXP. PART XL. — 1886.) Rr 208 



