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



broad as the bars, iliddle 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 ^'ery thin bars. Surface quite smooth. Both medullary shells lenticular. (May be 

 regarded in a phylogenetic as well as an ontogenetic sense, as the further de\'elopmental form of 

 Dcsmocam.pc cakmda and Ommatocamjx polyarthra.) 



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

 outer 0"27 ; gi-eatest breadth of the first O^Oo, of the second 0'09, of the third 0'12 ; pores of the 

 inner cortical shell 0-005, of the middle 0-004, of the outer O'OOS to 0-012 ; bars of the fir.st O-OOIi, 

 of the second 0-002, of the third 0-001. 



Habitat. — Pacific, central area, Station 266, depth 2750 fatlioms. 



2. Zygocampe corasiinn, u. sp. 



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

 chamljers 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. ]\Iiddle 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 sjaongy manner with the middle (or also witli the inner). Surface covered with 

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

 a pliylogenetic and ontogenetic sense as a further developmental stage of Dcsmocampe aphrodifi 

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



DiTnensions. — Length of the six-chambered inner cortical shell ()-24, of the middle 0-3, of tlie 

 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 0-003 to 0-015, of the third 0-01 to 0-05 ; bars corre- 

 .sponding 0-005 or 0-003 or 0-001. 



Habitat. — Xorth Pacific, Station 253, depth 3125 fathoms. 



3. Zygocampe (■liryscdkU>nii, ii. sp. (PL 40, fig. 13). 



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

 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. IMiddle cortical sliell 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 Ijreadth of the chambers decreases gradually towards both poles, so that 

 the whole shell assumes a spindle form. Sometimes on l)Oth pfiles is developed a short conical 



