60 - COELENTERATA—SPONGIAE CLASS I 
convoluted wall. Folds separated on outer surface by deeply incised furrows, 
on inner surface by shallow furrows. Framework extremely regular. Root 
and dermal layer absent. Upper Jurassic. 
Ventriculites, Mant. (Fig. 79). Bowl-, plate-, beaker-, funnel-shaped, or 
cylindrical, with wide cloaca. Wall thin, convoluted ; folds separated on both 
sides by closely crowded longitudinal furrows. Lattice-work of skeleton more 
or less regular; outer layer thickened; roots present. Common in Middle 
and Upper Cretaceous. 
Schizorhabdus, Rhizopoterion, Polyblastidium, Zitt. ; Sporadoscinia, Pomel ; Lepi- 
dospongia, Roem., etc. Cretaceous. 
Family 5. Coeloptychidae. Zittel. 
Umbel- or mushroom-shaped, with stalk. Wall thin, deeply folded. Convolutions 
radially arranged, becoming furcate toward periphery of umbel, and exposed on lower 

Fic. So. 
Cocloptychium agaricoides, Goldf. Upper Cretaceous ; Vordorf, near Braunschweig. A, Top view. JB, Pro- 
file. C Under surface, 2/3 natural size. D, Skeleton, 60/; 
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. 
Framework very regular; intersection nodes octahedral, perforated; rays of hexactins 
provided with slender, thorny processes. 
Coeloptychium, Goldf. (Fig. 80), occurring in the Upper Cretaceous of 
Northern Germany, England, and Southern Russia, is the solitary genus. 
