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



irregular, roundish pores, once to five times as broad as the bars. On the base of each distal chamber 

 (beginning in the second or third pair) a circle of twelve to sixteen larger square pores. Both 

 medullary shells compressed lenticular. (Eesernbles the inner cortical shell of Desmartus larvalis, 

 PI. 40, fig. 12, but is without the polar tubes and the outer envelope of this species.) 



Dimensions. Length of the six-chambered cortical shell 0'23 ; greatest breadth of each chamber 

 0'07 ; pores 0'002 to O'Ol, bars O002. 



Habitat. Cosmopolitan ; Mediterranean, Atlantic, Pacific, in various depths. 



Subgenus 2. Ommatocampula, Haeckel. 



Definition. Surface of the cortical shell thorny or spiny, but without peculiar 

 polar spines and without regular coronals of spines. 



4. Ommatocampe erucceformis, n. sp. 



Cortical shell with spiny surface, composed of six to twelve chambers of nearly the same size and 

 form, the distal chambers a little smaller. The form and structure of the cortical shell is nearly 

 the same as in the foregoing species, only the pores are somewhat larger, and the whole surface is 

 covered with bristle-like radial spines, about half as long as the breadth of one chamber. Both 

 medullary shells compressed and lenticular. 



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

 0-08 ; pores 0'005 to 0-012, bars 0'002. 



Habitat. North Atlantic, Canary Islands, Station 353, depth 2965 fathoms. 



5. Ommatocampe nereis, n. sp. (PI. 40, fig. 10). 



Cortical shell with spiny surface, composed of six (or more) chambers of different size and 

 structure. Both proximal chambers kidney-shaped, with subregular, circular, hexagonally framed 

 pores, twice as broad as the bars. All following chambers cap-like, with much smaller, irregular, 

 roundish pores, at the base of every chamber a circle of ten to twelve large square pores. Spines 

 of the surface short, irregularly scattered. Both medullary shells spherical. (All the observed 

 specimens possessed only six chambers.) 



Dimensions. Length of the six-chambered cortical shell 0'25 ; greatest breadth of each chamber 

 0'08 ; pores of both proximal chambers O'Ol, bars O'OOS ; basal pores of the other chambers 0'02 ; 

 pores of their distal caps O'OOS to O'OOG, bars 0'003. 



Habitat. Pacific, central area, Stations 271 to 274, depth 2350 to 2750 fathoms. 



Subgenus 3. Ommatocorona, Haeckel. 



Definition. Surface of the cortical shell spiny, on every chamber a regular circle 

 or coronal of radial spines. 



