ORDER IV 



SILICISPONGIAE— HEXACTINELLIDA 



67 



Lepidospongia Roemer ; Leiostracosia, Pledodermafium, Microhlastidium Schram- 

 men, etc. Cretaceous. 



Family 5. Ooeloptychidae Zittel. 



Umbel- or mushroom-shaped, with stalk. Wall thin, deeply folded. Convolutions 

 radially arranged, becoming furcate toward periphery of umbel, and exposed on lower 

 surface. Marginal and 

 upper surface enveloped 

 with porous dermal layer 

 entirely covering the folds. 

 Ostia only- on under side 

 of umbel, situated on 

 backs of the folds. Frame- 

 work very regidar ; inter- 

 section nodes octahedral, 

 perforated ; rays of hex- 

 actins provided with 



slender, thorny processes. PlocoscvphiapertusaGem.\ GreensancUCenomanian); Bauowitz, Kunsary. 



^ ' , 1 ■ rt,lFragment in natural size Wh, Dermal layer, five times enlarged ; c, Skeleton 



LoetoptyC Ilium of interior, i^/ii; d, Outward portion of skeleton, la/j. 



Goldf. (Fig. 76), oc- 

 curring in the Upper Cretaceous of Northern Germany, England, and Southern 

 Russia, is the solitary genus. 



Family 6. Maeandrospongidae Zittel. 



Sponge body consisting of thin-walled, intricately labyrinthine, and partially 

 amalgamated tubes or foliae, which form tuberous, pyriform, beaker-shaped, or bush- 

 like branching stocks. 

 Between the tubes are 

 cavities and interstices 

 of considerable size, 

 which constitute the so- 

 called inter canalicular 

 system. Four canals 

 faintly developed. Der- 

 mal layer absent, or re- 

 presented by a continuous 

 silicious superficial skin. 

 Abundant in the Cre- 

 taceous, and also re- 

 presented by numerous 

 recent genera. 



Plocoscyphia Reuss 



Becksla sokdandi Schliit. Quadratenkreide ; Coesfeld, Westphalia. A, CPiq 77) CluniD-like 

 Sponge body, 1/2 natural size ; 0, Ostia of radial canals ; /, Hollow, root-like , * , 



processes of wall. B, Skeleton, 50/j. Or bulboUS StOcks con- 



sisting of labyrinthic, 

 anastomosing tubes or foliae. Walls of tubes thin, perforated by numerous 

 small ostia. Latticed skeleton, intersection nodes solid or perforate. Cre- 

 taceous. 



Fig. 78. 



Becksia Schliiter (Fig. 78). 



The thin walls of the shallow, beaker-like 



