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



Genus 30. Tribonosphcera, 1 Haeckel, 1881, Prodromus, p. 471. 



Definition. C ollosphserida with simple shells, on the inside with radial 

 centripetal beams. 



The genus Tribonosphcera differs from Collosphcera by a very peculiar and rare 

 character, the development of centripetal radial sticks on the internal face of the shell ; 

 these beams are not united in the centrum, but finish freely in a certain distance 

 from it. 



1. Tribonosphcera centripetalis, n. sp. (PI. 5, fig. 12). 



Shell roundish or subspherical, with numerous small circular or roundish pores, about twice as 

 broad as the bars. Twenty to thirty pores on the half meridian of the shell. Outside of the shell 

 smooth, inside a variable number (ten to twenty) of thin, radial, centripetal sticks or spines, one- 

 third or one-half as long as the radius of the shell. (In the central capsule many very large 

 crystals, resting after the destruction of the capsule.) 



Dimensions. Diameter of the shell 01 to 012, of the pores O'OOS to 0'005, of the bridges O'OOl 

 to 0-002 ; length of the inner centripetal sticks 0'02 to 0'03. 



Habitat. Central Pacific, Station 271, surface. 



Genus 31. Pharyngosphcera , 2 n. gen. 



Definition. Coll o sphser id a with simple shells, having on the inside radial 

 centripetal tubes, the walls of which are solid. 



The genus Pharyngosphcera differs from Collosphcera, by the development of 

 radial tubules on the inside of the shell, which are directed centripetally towards 

 its centre. The wall of the tubule is solid, not latticed as in the following genus. 



1. Pharyngosphcera stomodcea, n. sp. (PL 5, fig. 10). 



Shell irregular polyhedral, with ten to fifteen polygonal faces and rounded edges. Pores very 

 small, circular, irregularly scattered, smaller than the bars. Twelve to fifteen pores on the half 

 meridian of the shell. On the inside of every shell-face one short, nearly cylindrical, centripetal 

 tubule, twice as long as broad, and about one-third as long as the shell radius. Outer umbilical 

 mouth of the tubules somewhat wider than the inner truncated mouth. 



Dimensions. Diameter of the shell Oil to 012, of the pores O'OOS to 0'005, of the bars O'Ol to 

 02 ; length of the inner tubuli 0'02, breadth of them O'Ol. 



Habitat. South Pacific, Station 288, depth 2600 fathoms. 



1 Tribonosphcera Cloak-sphere ; rji'/3a>, atfau^at. 2 Pharyngosjiluera = Throat-sphere ; (pxt>vy%, aipaija. 



