1630 THE VOYAGE OF H.M.S. CHALLENGER. 



be derived from it by elevation of the hexagonal pyramids, which in the latter lie in the spherical 

 plane). 



Dimensions. Diameter of the sphere 4'4 ; pyramidal tubes 0'25 long, O'Ol broad. 



Habitat. Indian Ocean, Cocos Islands (Rabbe), surface. 



10. Auloscena serrata, n. sp. (PI. 110, fig. 5). 



Radial tubes spindle-shaped, tapering towards both ends, thorny, twice as long as the thorny 

 pyramidal tubes ; armed at the distal end with an elegant corona which is composed of twelve to 

 sixteen curved terminal branches, Each branch bears two opposite series of small recurved teeth 

 and a terminal spathilla of six to eight larger recurved teeth. 



Dimensions. Diameter of the sphere 3'0 ; pyramidal tubes 0'3 long, O012 broad. 



Habitat. South Pacific, Station 298, depth 2225 fathoms. 



Genus 685. Aulopleyma, 1 Haeckel, 1879, Sitzungsb. med.-nat, Gesellsch. 



Jena, Dec. 12, p. 6. 



Definition. A ulosphserida with triangular meshes in the network, the tubes 

 of which are connected in different directions, and form the spongy wall of a 

 spherical shell. Radial tubes arise on the surface at the nodal points. 



The genus Auloplegma, one of the rarest forms of Aulosphserida, differs from the 

 preceding genera in the spongy structure of the lattice -sphere, the thickened wall of 

 which is composed of a loose framework. Numerous tubes, irregularly disposed in 

 different directions, are connected at the nodal points of this loose spongy framework, 

 whilst radial tubes arise on the surface of the latter. Auloplegma exhibits therefore a 

 relation to Aulosphcera, its probable ancestral form, similar to that which Pleymosphcera 

 does to Acanthosphcera among the Sphseroidea. 



1. Auloplegma perplexum, n. sp. (PL 111, figs. 8, 8a). 



Radial tubes straight, cylindro-conical, armed with six to eight verticils of lateral branches, 

 which increase in size towards the base ; each verticil is a cross of four dichotomous delicate 

 ramules, ending with a spinulate knob. The length of the radial tubes is about equal to the radial 

 diameter of the spongy framework, which forms the thick wall of the spherical shell, and is 

 composed of smooth and straight cylindrical tubes. 



Dimensions. Diameter of the shell 1'5 to 2'0, of ifs wall 0'3 to 0'4 ; length of the radial tubes 

 0-2 to 0-3, basal breadth O015. 



Habitat. North Pacific, Station 237, surface. 



1 A ulopleyma = Tubular framework ; <tixo'{, 



