ORDER IV 



SILICISP()X(JIAE-HEXACTINELLIDA 



r,o 



Zitt. Funnel-shaped or plate-like, with broad and shallow 

 cloaca, into which the large, round postica of short canals open. Inner and 

 ..liter surfaces provided with dermal layer, in which stellate spicules are em- 

 bedded with reduced externally 

 and internally directed rays. 

 Upper Jurassic. 



Casearia, Quenst. ( V I i 1 1 

 drical, with numerous annular 

 constrictions. Cloaca deep, 

 tubiform ; dermal layer re- 

 latively thick, and made up 

 of cemented stellate spicules. 

 Upper Jurassic. C. articulafu, 

 Goldf. sp. 



Porospongia, $ Orb. (Fig. 77). 

 Compressed and expanded, Flo . 77 . 



more rarely bulbous or cylin- 



Porospongia impressa, Golclf. sp. 

 imconia. a, 

 e, Skeleton, M/ 



Upper Jurassic; Muggendorf, 



drical. Superior surface pitted Fra '*?. A Fra s ient in natliral size = D ' 



with large exhalent apertures 

 of short, blindly terminating cloacae, and covered over with a dense or finely 

 perforate silicious skin, in which cruciform spicules and regular hexactins are 

 embedded. Lattice skeleton with cubical meshes ; intersection nodes imper- 

 forate. Upper Jurassic. 



Family 4. Ventriculitidae. Toulmin Smith. 



Wall intricately convoluted ; folds radially disposed, generally vertical in direc- 

 tion. Radial canals ending blind. Longitudinal furrows developed along folds of 

 the wall, and either open, or partially covered 

 over with dermal layer, which is usually 

 formed by thickening of the outer skeletal 

 layer. Skeletal framework, with octahedrally 

 perfoi'ated nodes. Roots consisting of elon- 



Zltt. Up , 



ma. ", Sponge, I/a natural size ; ?>, Skeleton, is/,. 



Fcu*yteia*smaCarteri.Zltt. Upper Jurassic; Hohenpiilz, 

 I 



Ventriculites striatvs, Smith. Quadratenkrciilc; 

 Linden, near Hanover, a, Sponge, i/., natural 

 size ; b, Transverse section, i/, ; c, .Ski-l.-fmi, U/j. 



gated silicious fibres united by transverse bridges and ivithout axial canals. Jurassic 

 and Cretaceous. 



Pachyteichisma, Zitt. (Fig. 78). Turbinate or bowl-shaped, with very thick, 



