1658 THE VOYAGE OF H.M.S. CHALLENGER. 



Subgenus 4. Challengerosium, Haeckel. 



Definition. — Margin of the shell dentated or serrated, with a continuous series of 

 numerous short radial spines. 



17. Challenger on channeri, John Murray. 



Challengeron clianneri, Jolm Murray, 1879, in litteris, Narr. Chall. Exp., vol. i. p. 226, pi. A, 

 fig. 12. 



Shell subcircular, lenticular, strongly compres.sed, with fourteen to eighteen slender, straight, 

 radial spines on the margin ; the spines are straight, equidistant, cylindrical, and about as long as 

 the radius of the shell. Peristome short, with two parallel, vertical, lateral, straight teeth, which are 

 less than half the length of a spine. 



Dimensions. — Diameter of the shell 014 to 017 ; length of the spines 0-06 to 0-08. 



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



18. Challengeron moseleyi, n. sp. (PL 99, fig. 14). 



Shell circular, lenticular, strongly compressed, with tliirty to forty slender, straight, equidistant, 

 radial spines on the margin, larger and smaller spines alternating; the larger spines are about as 

 long as the radius, the smaller only half as long. Peristome short, tubular, with two divergent 

 ovate or nearly triangular teeth, a dorsal and a ventral, about as long as the shorter marginal spines. 



Dimensions.- — Diameter of the shell 013 to 015; length of the larger spines 0"6 to 0'07, of the 

 smaller 0-03 to 0-04. 



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



19. Challengeron hethelli, John Murray. 



Challengeron hethelli, John Murray, 1879, m litteris, Narr. Chall. Exp., vol. i. p. 226, pi. A, 

 fig. 6. 



Shell subcircular, lenticular, strongly compressed, with numerous (twenty to thirty) short 

 conical spines on the margin (often wanting in the upper part of the dorsal margin). Peristome 

 with a deep labial incision and two parallel triangular lateral teeth, the upper margin of which 

 is horizontal. 



Dimensions. — Diameter of the shell 0'2 to 0'25; length of the spines 0'02 to 0'03. 



Habitat. — North Pacific, Stations 238, 241 (off Japan), depth between 2300 and 3950 fathoms. 



20. Challengeron hathyhium, n. sp. 



Shell subcircu^lar, lenticular, slightly compressed, with a corona of nimierous (thirty to forty or 

 more) short, conical, radial spines on the margin. Peristome helmet-shaped, nearly as long as the 



