EEPORT ON THE EADIOLARIA. 69 



the central point of the shell are united about twelve (?) thin and straight radial beams, which are 

 forked, with dichotomous branches ; the distal ends of the branches are inserted in the corners of 

 the hexagons on the inside of the shell. 



Dimensions. — Diameter of the shell 015, pores 0"02, bars 0'003. 



Habitat. — Central Pacific, Station 271, surface. 



Genus 17. Ethmosiihwra} Haeckel, 1862, Monogr. d. Radiol., p. 349. 



Definition. — L i o s p h se r i d a with oue single latticed sphere, with simple shell- 

 cavity ; with shell-pores which are prolonged on the outside in centrifugal, conical, or 

 cylindrical tubuli. 



The genus Ethmosphcera differs from the simple Cenosphcera, its ancestral form, by 

 the peculiar formation of the shell-pores ; in all observed species of the genus these are 

 quite regular, of nearly equal size and form ; their base in the spherical shell-face is 

 hexagonal, but on the outside prolonged into centrifugal, external, radial tubuli, which 

 are either conical or cylindrical (in the latter case both openings of the tubes being equal, 

 in the former the outer opening being smaller than the inner). The solitary Ethmos- 

 phcera corresponds to the social Siphonosphcera ; but in the former the formation of 

 the shell and of its tubuli is quite regular, in the latter more or less irregular. 



Subgenus 1. Etlimosphcerella, Haeckel. 

 Definition. — Tubuli conical, their outer opening smaller than the inner. 



1. Ethmosphcera siphonophora, Haeckel. 



Ethmosphcera siphonophora, Haeckel, 1862, Monogr. d. RadioL, p. 350, Taf. xi. fig. 1. 



Tubuli conical, their outer opening half as broad as the inner and three tunes as broad as their 

 height. Five to six pores on the quadrant. Diameter of the outer pores one and a half times as 

 large as their distance from each other. 



Dimensions. — Diameter of the shell O'l, outer pores O'Ol, their distance O'OOV. 



Habitat. — Mediterranean (Messina), surface, Haeckel. 



2. Ethmosphcera conosiphonia, n. sp. (PL 12, figs. 5, 5(i). 



Tubuli conical, their outer opening two thirds as broad as the inner, and scarcely broader than 

 their height. Ten to twelve pores on the quadrant. Diameter of the outer pores twice as large as 

 their distance from each other. 



Dimensions. — Diameter of the shell Ol7, outer poi-es O'Ol, their distance 0"005. 



Habitat. — Central Pacific, Station 268, depth 2900 fathoms. 



1 Ethmosphcera = Sieve-spbere ; ii^fio;, a^ui^a. 



