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



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

 plane). 



Dimensiom. — Diameter of the sphere 44 ; pyramidal tubes 025 long, 0-01 broad. 



Habitat. — Indian Ocean, Cocos Islands (Eabbe), surface. 



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



Eadial 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. 



DimeTisions. — Diameter of the sphere 3-0; pyramidal tubes O'S long, 0012 broad. 



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



Genus 685. Atdoplegma,'^ Haeckel, 1879, Sitzungsb. med.-nat. Gesellsch. 



Jena, Dec. 12, p. 6. 



Definition. — A u 1 o s p h as r i d a 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 Atdoj^legma, one of the rarest forms of AulospliEerida, 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 Anlosphwra, its probable ancestral form, similar to that which PlegmosphcBoxt 

 does to Acanthosphcera among the Sphseroidea. 



1. Auloplegma perplexum, n. sp. (PI. Ill, figs. 8, 8a). 



Eadial 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 its wall 0-3 to 04 ; length of the radial tubes 

 0-2 to 0-3, basal breadth 0015. 



Habitat. — North Pacific, Station 237, surface. 



1 Aul(ypUrjma = 'S\xhvi\&T framework ; aiXoV, wAiy^*. 



