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



Subfamily Clatheosph.eeida, Haeckel, 1881, Prodromus, jj. 472. 



Definition. — C ollosphserida with a double lattice-sheU around every central 

 capsule of the coenobium ; both concentric shells connected by irregular or subradial 

 beams, commonly solid or lamellar staffs, rarely hollow tubes. 



Genus 43. Clathrosphcera,^ Haeckel, 1881, Prodi'omus, p. 472. 



Definition. — Colic sphser id a with a double lattice-shell around every central 

 capsule of the coenobium ; surface of the outer shell smooth. 



The genus Clathrosphcera (with smooth surface) and the following Xanthiosphcera 

 (with spiny surface) form together the small subfamily, Clathrosphaerida, different 

 from the other CoUosphserida by the double lattice-shell. From the surface of the inner 

 primary shell arise either solid spines or hollow tubes, which unite by the anastomosis 

 of irregular branches and so form the outer secondary shell, often very incomplete 

 and irregular. All Clathrospheerida seem to inhabit great depths. 



Subgenus 1. ClathrosplicBrula, Haeckel. 



Definition. — The connecting staffs between both shells are hollow tubes (derived 

 from Sip}honosphcera). 



1. Clathrosphcera circumtexta, n. sp. (PI. 8, fig. 6). 



Inner shell spherical, with irreguhir roundish large meshes, now broader now smaller than their 

 liai's. Eight to ten meshes in the half meridian of the shell. All these meshes are prolonged into 

 short eyhndrical hollow tubes, about as long as broad, somewhat constricted in the middle. From 

 the margins of the outer openings of these tubes proceed very numerous and delicate siliceous 

 filaments, which all lie on the same spherical face, braneli, anastomose, and twine over the openings 

 and the intervals between them, forming a very thin, arachnoid spherical outer shell. The meshes 

 of this are quite irregular polygonal, of very different size and form. The radius of the inner 

 shell bears to that of the outer a ratio = 5:6. 



DimensioTis. — Diameter of the inner shell Oil to 0'13, of the outer 0"13 to 0'16 ; meshes of 

 the inner shell 0-005 to 0-02, of the outer 0005 to 0-04. 



Habitat. — North Pacific, Stations 238 to 253, depths 2050 to 3950 fathoms. 



Subgenus 2. Clathrosphceriimi, Haeckel. 



Definition. — The connecting staffs between the two shells are solid rods or lamellar 

 spines (derived from Acrosphcera). 



1 Clathrosphcera = Lattice-sphere. 



