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



broad as the bars. Middle cortical shell cylindrical, hemispherical at both poles, with subregular 

 circular pores, somewhat smaller than those of the inner ; the bars also thinner. Outer cortical 

 shell of the same form as the middle, but with very delicate network, and quite irregular, roundish 

 pores and very thin bars. Surface quite smooth. Both medullary shells lenticular. (May be 

 regarded in a phylogenetic as well as an ontogenetic sense, as the further developmental form of 

 Desmocampe catenula and Ommatocampc polyarthra.) 



Dimensions. Length of the six-chambered inner cortical shell 0'17, of the middle - 22, of the 

 outer 027 ; greatest breadth of the first 0'05, of the second 0'09, of the third O12 ; pores of the 

 inner cortical shell O'OOS, of the middle 0004, of the outer 0'003 to 0'012 ; bars of the first 0'003, 

 of the second 0'002, of the third O'OOl. 



Habitat. Pacific, central area, Station 266, depth 2750 fathoms. 



2. Zygocampe corasium, n. sp. 



Inner cortical shell with six to eight chambers of different size and form. Both proximal 

 chambers kidney-shaped, with five to six transverse rows of subregular, circular, hexagonally 

 framed pores, twice as broad as the bars. All following chambers cap-like, the distal somewhat 

 smaller ; their pores much smaller, irregular, roundish ; only at the base of each chamber a circle, 

 of ten to twelve large square pores. Middle cortical shell cylindrical, in the equatorial zone a little 

 constricted, hemispherical at both poles, with irregular delicate network of roundish, polygonal 

 meshes. Outer cortical shell of the same form as the middle, but with a very delicate and quite 

 irregular network of polygonal meshes. Commonly this outer mantle is incomplete, and sometimes 

 interwoven in a spongy manner with the middle (or also with the inner). Surface covered with 

 many irregular, thin, bristle-like spines. Both medullary shells lenticular. (May be considered in 

 a phylogenetic and ontogenetic sense as a further developmental stage of Desmocampe aphrodite 

 and Ommatocampc nereis, PI. 40, fig. 10.) 



Dimensions. Length of the six-chambered inner cortical shell 0'24, of the middle O3, of the 

 outer 0'36 ; greatest breadth of the first 0'08, of the second 0'12, of the third 0'16; pores of the first 

 (on an average) 0'005 to 0'02, of the second O003 to 0'015, of the third O'Ol to (H)5 ; bars corre- 

 sponding 0-005 or 0-003 or O'OOl. 



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



3. Zygocampe chrysalidium, n. sp. (PL 40, fig. 13). 



Inner cortical shell with six to eighteen chambers of different size and form. Both proximal 

 chambers kidney-shaped, with six to seven transverse rows of subregular, circular pores, three to 

 four times as broad as the bars. All following chambers with more irregular pores, with a circle 

 of ten to twelve larger square pores at the base. Middle cortical shell with smaller, irregular, 

 roundish pores. Outer cortical shell with larger polygonal, quite irregular pores. Both outer shells 

 appear commonly incomplete or somewhat irregularly developed, and sometimes in a spongy manner 

 interwoven with one another. Surface covered with irregular, bristle-like spines. Both medullary 

 shells spheroidal. The breadth of the chambers decreases gradually towards both poles, so that 

 the whole shell assumes a spindle form. Sometimes on both poles is developed a short conical 



