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



Family 9. Cceloptychid.e, Zittel. 



Sponge body umbel-like, stalked. Wall thin, deeply folded ; the central cavity 

 divided into radial chambers. Upper surface shallow or deepened, entirely enveloped 

 by a continuous dermal layer which usually consists of variable coarse and finely porous 

 strands. Canalicular ostia only on the under side of the umljel, on the backs of the 

 folds, sometimes also on the stalk. Lattice framework with large, regular, cubical 

 meshes. The intersection nodes of the amalgamated six-rayed spicules octahedral, 

 perforated. The radii of the six-rayed spicules bear thorny and root-like protuberances. 



Example. — The single fossil genus Cveloj^tychium. 



Suborder II. LYSSACINA. 



The whole skeleton consisting of spicules which are bound together only by sarcode 

 (exceptionally also by a smooth siliceous substance in iiTegular ways). Flesh spicules 

 usually present in rich abundance and much differentiated. 



Family 1. M on acid. ^, Marshall. 



Whole sponge body composed of similar spicules. 



Examples. — Acanthospongia, Salt, and Stauractinella, Zittel. 



Family 2. Pleionacice, Marshall. 



Main portion of the skeleton composed of six-rayed spicules and also of forks and 

 rosettes. 



Examples. — The living genera Asconema, Kent, and Lanuginella, Schmidt. 



Family 3. Pollacid^, Marshall. 



Form of skeleton and flesh sj)icules very variable. Siaeeial dermal skeleton and 

 inner lining of the gastral cavities present. Base usually forming a root-tuft of long 

 siliceous spicules. 



Examples. — The living genera Holtenia, Schmidt, Pheronema, Leidy, Cratero- 

 morplia, Gray, Rossella, Carter, Sympagella, Schmidt, Placodictyon, Schmidt, Eiqjlec- 

 tella, Owen, Hahrodictyum, Wyv. Thomson, Laharia, Gray, Semperella, Marshall 

 {Meyerina, Gray), Hyalonema (Carteria), Gray, and 1 Acestra, Eoem, from the 

 Silurian. 



In the report which Marshall and Meyer' made in 1877 on the Philippine Hexac- 



' Miitheilungen aus d. Konigl. Zool. Museum in Dresden, 1877, p. 263. 



