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



bristle-like spiaes. On both poles of the main axis a bunch of six to eight aggregated larger 

 conical spines, about as high as a single chamber. 



Dimensions. — ^Main axis (without polar spines) 0-2, equatorial axis 0-06 ; pores 0-005 to 0-015, 

 bars 0-003 ; length of the polar spines 0-05, basal thickness 0-005. 



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



4. Panicium coronatum, n. sp. (PI. 40, fig. 4). 



Both proximal chambers kidney-shaped, covered with short stout spines. Pores irregular, 

 roundish, twice to four times as broad as the bars ; seven to eight on the half meridian, eleven to 

 thu-teen on the half equator of each chamber. Both distal chambers cap-Uke, separated from the 

 former by a circle of ten to twelve very large square pores ; the other pores very small, roundish. 

 The circumpolar area is smooth, surrounded by a circle of ten to twelve very stout, conical, radial 

 spines, which arise from the distal ends of the bars separating the large square meshes. 



Dimensions. — Main axis (without spines) 0-22, equatorial axis 0-08 ; greatest breadth in the 

 equator of the chambers 0-1 ; pores of the proximal chambers 0-007 to 0-015, bars 0-004 ; square 

 pores of the distal chambers 0-02 to 0-03, small pores 0-005, bars 0004 ; length of the radial 

 spines of the polar circles 0-07, basal thickness 0-007. 



Habitat. — Pacific, central area, Station 271, depth 2425 fathoms. 



Genus 166. Perijyanicium^ n. geu. 



Definition. — P a n a r t i d a with double cortical shell and double medullary shell, 

 on both poles of the main axis with two opposite apical spines, or with a bunch or circle 

 of polar spines. 



The genus Peripaniciiim differs from Panicium only in the development of an 

 outer reticulated envelope, which mantle-like surrounds the shell, and represents a second 

 or external cortical shell. As in Panicium, its ancestral form, so also in Peripanicium, 

 there can be distinguished two subgenera: — Peripanicea, where only a single large 

 spine arises from each pole (lying in the main axis), and Peripanicula, where a variable 

 number of spines is to be found, either diverging bunch-like from the pole itself, or 

 surrounding it as a crown-like polar cii-cle. 



Subgenus 1. Peripanicea, Haeckel. 

 Definition. — On both poles of the main. axis only a single large spine. 



1. Peripanicium amjihixiphus, n. s^j. 



Internal cortical shell with four unequal chambers, with thorny surface. Both proximal 

 chambers kidney-shaped (with subregular hexagonal pores, three tunes as broad as the bars). 



1 Peripanicium = Panicium with mantle. 



