418 M. K. A. Zittel on Fossil HexactinelUda. 



Family 5. Ventriculitidae. 



Sponge-body simple or polyzoic, cup-shaped, fminel-shaped, 

 cylindrical, top-shaped or branched. Wall maeandrically 

 folded. Latticed framework with octahedrally perforated 

 crossing -nodes. Canal -system generally well-developed. 

 Radial canals csecal. Both surfaces with ostia or longitudinal 

 furrows. Covering layer rarely deficient, generally produced 

 by thickening of the outer skeletal layer. Eoot consisting of 

 elongated siliceous fibres without axial canals, united by 

 transverse bridges. 



a. Without root. 

 Pachyteichisma, Zitt. Jura. 

 TrochoholuSj Zitt. Jura. 



b. With root. 



Ventriculites, Mant. Cretaceous. 

 Schizorhabdus, Zitt. Cretaceous. 

 Tretostamnia, Pomel. Miocene. 

 Hhizopoterion, Zitt. Cretaceous. 

 Spo7'adoscinia, Pomel. . Cretaceous. 

 Licmosinion J Pomel. Cretaceous. 

 Polyhlastidium, Zitt. Cretaceous. 



c. Upper margin of the cup with a finely porous covering 



layer. 

 Cephalites, T. Smith (p. p.). Cretaceous. 



d. Outer surface furnished with a dense siliceous coat. 

 Lepidospongia, Rom. Cretaceous. 



Family 6. Staurodermidae. 



Sponge-body top-shaped, cup-shaj^ed, cylindrical, rarely 

 branched. Latticed skeleton more or less regular. Crossing- 

 nodes solid or octahedrally perforated. Outer or both surfaces 

 of the wall furnished with stellate spicules, which diifer in 

 form from those of the rest of the skeleton, and are either only 

 loosely cemented to one another, or imbedded in a connected 

 siliceous coat. 



a. Canal-system well-developed. Sponge-body cup-shaped, 

 cylindrical or branched. 

 Cypelliaj Pomel, Jura. 

 Stauroderma, Zitt. Jura. 

 Porocypellia, Pomel. Jura. 

 Casearia, Queust. Jura. 

 h. Canal-system slightly developed. Sponge-body lamel- 

 liform. 

 Porospongia, D'Orb. Jura. 

 Ophrystoma, Zitt. Cretaceous. 

 '^Placochlcenia. Pomel. Miocene. 



