1364 THE VOYAGE OF H.M.S. CHALLENGER. 



are prolonged over the shell-base into three pyramidal, hollow and fenestrated feet, the lower edge 

 of which is horizontal. Pores regular, circular, of equal size in the thorax and abdomen. 



Dimensions. Length of the three joints, a 0'02, b 0'02, c 0'09 ; breadth, a 0'03, I 0'05, c 01. 



Habitat. Fossil in Barbados. 



6. Lithochytris lucerna, n. sp. (PI. 67, fig. 14). 



Shell three-sided pyramidal, with two indistinct strictures. Length of the three joints = 1:2:5, 

 breadth = 2:3:8. Cephalis small, with a horn of the same length, conical. Thorax with sub- 

 spherical cavity. Abdomen with three rounded, prominent edges, which are prolonged over the 

 shell-base into three conical, hollow, and fenestrated feet, twice as long as the thorax, with a thick, 

 pyramidal, terminal spine. Pores subregular, circular, of equal size in the thorax and abdomen. 



Dimensions. Length of the three joints, a 0'02, b 0'04, c 01 ; breadth, a 0'04, b 0'06, c 016. 



Habitat. South Pacific, Station 297, depth 1775 fathoms. 



7. Lithochytris lanterna, n. sp. (PI. 67, fig. 11). 



Shell three-sided pyramidal, with two distinct strictures. Length of the three joints = 1:2:4, 

 breadth = 1:3:6. Cephalis small, with a pyramidal slender horn of twice the length. Thorax 

 with subspherical cavity. Abdomen with three sharp prominent edges, which are prolonged over 

 the convex shell-base into three slender, prismatic, hollow, fenestrated feet, strongly divergent, twice 

 as long as the thorax (seen in fig. 11 from the vaulted base). Pores circular, twice as broad in the 

 abdomen as in the thorax. 



Dimensions. Length of the three joints, a 0'02, b 0'04, c 0'08 ; breadth, a 0'02, b 0'06, c 012. 



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



8. Lithochytris pyramidalis, Ehrenberg. 



Lithochytris pyramidalis, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 76, Taf. v. 

 fig. 1. 



Shell three-sided pyramidal, without external strictures, but with two internal transverse 

 girdles. Length of the three joints = 1:2:6, breadth = 2:4:8. Cephalis with a short horn of 

 half the length, conical. Cavity of the thorax subspherical. Abdomen with three rounded edges, 

 prolonged over the concave base into three pyramidal, hollow, and fenestrated feet, twice as long as 

 the thorax. Pores large, irregular, roundish. 



Dimensions. Length of the three joints, a 0'02, b 0'04, c 012 ; breadth, a 0'04, b 0'08, c 016. 



Habitat. Central Pacific, Stations 265 to 268, depth 2700 to 2900 fathoms ; fossil in Barbados. 



9. Lithochytris pteropus, n. sp. (PI. 67, fig. 15). 



Shell three-sided pyramidal, with two indistinct strictures, but with two broad, internal girdles. 

 Length of the three joints = 2:2:6, breadth = 2:3:9. Cephalis with a small horn of half the 



