REPORT ON THE RADIOLARIA. 1649 



3. ChallengeHa sigmodon, n. sp. 



Shell circular, nearly spherical, slightly compressed. Peristome with a single simple tooth, 

 which is S-shaped, more or less curved, and about one-third as long as the shell. 

 Dimensions. — Diameter of the shell 0-3 to 04, length of the tooth 01 to 014. 

 Habitat. — North Pacific, Station 231, depth 2250 fathoms. 



4. Challengeria tritonis, n. sjj. (PI. 99, fig. 5). 



SheU ovate, slightly compressed. Peristome with a single simple tooth, which is vertical, straight, 

 slenderly conical, and about half as long as the shell. 



Dimensions. — Diameter of the shell 015 to 0-2, length of the tooth 01 to 012. 



Habitat. — North Atlantic, Fteroe Channel, Gulf Stream, in great numbers, in depths from 100 

 to 600 fathoms. (Expedition of H.M.S. " Triton," 1882), John Murray. 



5. Challengeria j^yramidalis, n. sp. 



Shell slenderly ovate, one and a half times as long as broad, slightly compressed. Peristome with 

 a single, simple, large tooth, which is three-sided pyramidal, vertical, straight, and longer than half 

 the shell. 



Dimensions. — Length of the shell 0-6 to 0-8, breadth 01 to 0'5 ; length of the tooth Ol to 0'5. 



Habitat. — South Atlantic, Station 318, depth 2040 fathoms. 



6. Challengeria cyrtodon, n. sp. 



Shell ovate, lenticular, strongly compressed. Peristome with a single simple tooth, which is 

 crescent-shaped, curved over the mouth, and about half as long as the shell. 



Dimensions. — Length of the shell 01 to 0"5, breadth 0^3 to 01 ; length of the tooth 0'2 to 0'25. 

 Habitat. — South Pacific, Station 289, depth 2550 fathoms. 



Subgenus 2. CJiallengeretta, Haeckel. 



Definition. — Peristome with a forked or bifid tooth, or with two parallel lateral 

 teeth (CJiallengericB diodontes). 



7. Challengeria sloggettii, John Murray (PI. 99, fig. 4). 



Challenejeria harstoni, John Murray, 1879 (partim), in litteris, Narr. ChaU. Exp., vol. i. 

 p. 226, pi. A, fig. U. 



Shell triangular, strongly compressed, with three rounded corners, or nearly semicircular ; its 

 aboral margin straight, horizontal, longer than the convex, dorsal, and ventral margins. Peristome 

 (ZOOL. CHALL. EXP. — PART XL. — 1886.) Er 207 



