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



1. Ommatartus amphicanna, n. sp. 



Cortical shell with spiny surface, composed of six chambers of equal size and kidney-shaped ; 

 every chamber with four to five transverse rows of irregular, roundish pores, twice to three 

 times as broad as the bars. Both medullary shells lenticular. Polar tubes conical, about as long as 

 one chamber, with smaller pores. Both medullary shells spheroidal, more or less compressed. 

 (Resembles Desmartus larvalis, PI. 40, fig. 12, but is without the external cortical shell.) 



Dimensions. Length of the six-chambered cortical shell 0'24; greatest breadth of each chamber 

 0-07 ; pores O'OOS to 0'012, bars 0-004 ; length of the polar tubes 0'04 to 0'05, basal thickness 0"02. 



Habitat Pacific, central area, Stations 270 to 274, depth 2350 to 2925 fathoms. 



2. Ommatartus amphisiphon, n. sp. 



Cortical shell with spiny surface, composed of six or eight chambers of different size and 

 form. Both proximal chambers kidney-shaped, each with five to six transverse rows of irregular, 

 polygonal pores, three to four times as broad as the bars. The other (four to six) chambers 

 somewhat smaller, more hemispherical, with smaller, irregular pores, but on the base of each a circle 

 of ten to twelve larger square pores. Polar tubuli prismatic, about half as long as the main axis, 

 with prominent edges and longitudinal rows of smaller pores between them. Both medullary shells 

 lenticular. (Eesembles closely Panarium tubularium, PI. 40, fig. 9, but with six to eight chambers 

 instead of four, and with longer tubuli.) 



Dimensions. Length of the six-chambered cortical shell 0'26 ; greatest breadth of the proximal 

 chambers 0'09, of the distal chambers 0'07; pores of the former O'Ol, of the latter 0'004; large square 

 pores 0-013, bars O'OOS ; length of the polar tubes O'l to 012, thickness 0'02. 



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



3. Ommatartus amphobolus, n. sp. 



Cortical shell with spiny surface, composed of six chambers of different size and form. Both 

 proximal chambers kidney-shaped, with four to five transverse rows of subregular, circular pores, 

 twice as broad as the bars. Both middle chambers cap-like, with a basal circle of ten to twelve 

 larger square pores, and small roundish pores on the cap. Both distal chambers smaller, conical, 

 with very small roundish pores. Polar tubuli conical, nearly half as long as the main axis, also 

 with very small pores. Both medullary shells lenticular. 



Dimensions. Length of the six-chambered shell 0'28, greatest breadth 0'08; pores of the 

 proximal chambers O'Ol, bars 0'005; pores of the distal chambers and the polar tubes 0'002 to 0'004, 

 bars 0-002; length of the polar tubes 013, basal thickness 0'03. 



Habitat. North Pacific, Station 253, depth 3125 fathoms. 



Genus 171. Desmocampe, 1 n. gen. 



Definition. Z ygartida with double cortical shell and double medullary shell, 

 without polar tubes. 



e --- Chain-like caterpillar; 



